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Villalobos Sambucaro MJ, Alzugaray ME, Ronderos JR. Mechanisms controlling haemolymph circulation under resting conditions in the Chagas disease vector Rhodnius prolixus. J Exp Biol 2024; 227:jeb247801. [PMID: 38989599 DOI: 10.1242/jeb.247801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Accepted: 07/05/2024] [Indexed: 07/12/2024]
Abstract
Chagas disease vectors can ingest several times their own volume in blood with each meal. This ad libitum feeding causes an intense process of diuresis, inducing the insect to eliminate a large quantity of urine and faeces. To ensure diuresis, the speed of circulation of the haemolymph is increased. The Triatominae circulatory system is quite simple, including the dorsal vessel, which pumps haemolymph in an anterograde direction. The return is caused by peristaltic contractions of the anterior midgut. Triatominae insects can spend several weeks without feeding, meaning that most of the time, the insect is in a resting condition. Although the mechanisms controlling the circulation of the haemolymph during post-prandial diuresis have been largely analysed, the mechanisms controlling it during resting conditions are poorly understood. In this study, we analysed several canonical pathways (i.e. L-type VGCC, GPCR, RyR, IP3R) and a novel system represented by the recently characterized Piezo proteins. Our results show that during the resting condition, haemolymph circulation depends on a cross-talk between myogenic activity, inhibitory and stimulatory cellular messengers, and Piezo proteins. This report also unveils for the first time the existence of a putative Piezo protein in Hemiptera.
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Affiliation(s)
- María José Villalobos Sambucaro
- Cátedra de Histología y Embriología Animal, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, 1900 La Plata, Buenos Aires, Argentina
- CONICET, Godoy Cruz 2290, CABA, Argentina
| | - María Eugenia Alzugaray
- Cátedra de Histología y Embriología Animal, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, 1900 La Plata, Buenos Aires, Argentina
- CONICET, Godoy Cruz 2290, CABA, Argentina
| | - Jorge Rafael Ronderos
- Cátedra de Histología y Embriología Animal, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, 1900 La Plata, Buenos Aires, Argentina
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José Villalobos Sambucaro M, Pacheco C, Rafael Ronderos J. Allatotropic peptides modulate muscle contraction of the female reproductive system in Rhodnius prolixus (STÄL). Gen Comp Endocrinol 2023; 343:114358. [PMID: 37567349 DOI: 10.1016/j.ygcen.2023.114358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 06/28/2023] [Accepted: 08/08/2023] [Indexed: 08/13/2023]
Abstract
Allatotropin (AT) acts as a myoregulator at the level of the dorsal vessel (DV) and midgut (MG) in triatominae insects. Previous analyses of the expression of the AT receptor in Rhodnius prolixus showed that AT is expressed in the DV and MG, but also in the reproductive system in females. To further study the activity of AT on female reproductive organs we analyzed the response by adult females in different physiological conditions, including unfed (virgin and mated), and fed mated females (gravid), to doses ranging between 10-14 and 10-6M. Myoregulatory activity was evaluated in vivo, by recording independently the frequency of contractions of each organ after treatment. The results show that the effect of AT varies depending on the organs and on the physiological state of the female. Whilst unfed virgin females did not show response to the peptide for neither of the applied doses, the ovaries showed a differential response, presenting the highest frequency of contractions in gravid individuals. An increase in the frequency of contractions of the oviducts was only observed in mated females. Uterus and spermathecae responded in both gravid and mated females, with maximum activity in the latter. In the bursa, responses were only detected in gravid females. The differential response of the organs seems to be associated to particular moments along the reproductive cycle, such as with the spermathecae that reacted to AT in both unfed mated and gravid females, when the movement of spermatozoids is physiologically crucial. Testes and accessory glands of the male, expressed the mRNA of AT precursor, suggesting that the male would modulate the contractile behavior of the female reproductive system after copula. The ovaries also expressed AT mRNA suggesting the existence of a paracrine/autocrine system modulating muscle contraction.
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Affiliation(s)
- María José Villalobos Sambucaro
- Cátedra de Histología y Embriología Animal, Facultad de Ciencias Naturales y Museo - Universidad Nacional de La Plata (FCNyM - UNLP), La Plata, Argentina; Concejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
| | - Cristian Pacheco
- Cátedra de Histología y Embriología Animal, Facultad de Ciencias Naturales y Museo - Universidad Nacional de La Plata (FCNyM - UNLP), La Plata, Argentina; Post-doctoral fellow (FONCyT), Argentina
| | - Jorge Rafael Ronderos
- Cátedra de Histología y Embriología Animal, Facultad de Ciencias Naturales y Museo - Universidad Nacional de La Plata (FCNyM - UNLP), La Plata, Argentina.
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3
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Capriotti N, Gioino P, Ons S, Ianowski JP. The neuropeptide RhoprCCHamide2 inhibits serotonin-stimulated transcellular Na+ transport across the anterior midgut of the vector of Chagas disease, Rhodnius prolixus. J Exp Biol 2021; 224:264938. [PMID: 34008838 DOI: 10.1242/jeb.242272] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Accepted: 03/31/2021] [Indexed: 12/12/2022]
Abstract
Rhodnius prolixus is a blood-feeding insect vector of Trypanosoma cruzi, a protozoan parasite that causes Chagas disease. During each blood meal, the animals ingest large volumes of blood, that may be up to 12 times the unfed body mass. These blood meals impose a significant osmotic stress for the animals due to the hyposmotic condition of the ingested blood compared with the insect's hemolymph. Thus the insect undergoes a massive postprandial diuresis that allows for the excretion of the plasma fraction of the blood in less than two hours. Diuresis is performed by the excretory system, consisting of the Malpighian tubules and gut, under the control of diuretic and anti-diuretic factors. We investigated the ion transport machinery triggered by stimulation with the diuretic factor serotonin in the anterior midgut (i.e. crop) and the effect of the diuretic modulator RhoprCCHamide2. Ussing chamber assays revealed that serotonin-stimulated increase in transepithelial short-circuit current (Isc) was more sensitive to the blockage with amiloride than 5-N-ethyl-N-isopropyl amiloride (EIPA), suggesting the involvement of Na+ channels. Incubation in Na+-free, but not Cl--free saline, blocked the effect of serotonin on Isc. Moreover, treatment with Na+-K+-2Cl- cotransporter (NKCC) and Na+-Cl- cotransporter (NCC) blockers had no effect on fluid secretion but was blocked by amiloride. Blockage of Na+/K+-ATPase with ouabain inhibited Isc but the H+-ATPase inhibitor bafilomycin had no effect. The neuropeptide RhoprCCHamide2 diminished serotonin-stimulated Isc across the crop. The results suggest that Na+ undergoes active transport via an apical amiloride-sensitive Na+ channel and a basolateral ouabain-sensitive Na+/K+-ATPase, while Cl- is transported through a passive paracellular pathway.
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Affiliation(s)
- Natalia Capriotti
- Laboratorio de Neurobiología de Insectos, Centro Regional de Estudios Genómicos, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Bvd 120 numero 1459, codigo postal 1900, La Plata, Buenos Aires, Argentina
| | - Paula Gioino
- Department of Anatomy, Physiology and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5E5
| | - Sheila Ons
- Laboratorio de Neurobiología de Insectos, Centro Regional de Estudios Genómicos, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Bvd 120 numero 1459, codigo postal 1900, La Plata, Buenos Aires, Argentina
| | - Juan P Ianowski
- Department of Anatomy, Physiology and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5E5
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Capriotti N, Ianowski JP, Gioino P, Ons S. The neuropeptide CCHamide2 regulates diuresis in the Chagas disease vector Rhodnius prolixus. ACTA ACUST UNITED AC 2019; 222:jeb.203000. [PMID: 31053646 DOI: 10.1242/jeb.203000] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 04/29/2019] [Indexed: 12/11/2022]
Abstract
Given that hematophagous insects ingest large quantities of blood in a single meal, they must undergo a rapid post-prandial diuresis in order to maintain homeostasis. In the kissing bug Rhodnius prolixus (Hemiptera: Reduviidae), the coordinated activity of the Malpighian tubules and anterior midgut maintains water and ion balance during the post-prandial diuresis. Three to four hours after the meal, the diuretic process finishes, and the animal enters an antidiuretic state to ensure water conservation until the next blood intake. The diuretic and antidiuretic processes are tightly regulated by serotonin and neuropeptides in this insect. In the present work, we report that the neuropeptide precursor CCHamide2 is involved in the regulation of the post-prandial diuresis in R . prolixus Our results suggest a dual effect of RhoprCCHamide2 peptide, enhancing the serotonin-induced secretion by Malpighian tubules, and inhibiting serotonin-induced absorption across the anterior midgut. To our knowledge, this is the first report of a hormone presenting opposite effects in the two osmoregulatory organs (i.e. midgut and Malpighian tubules) in insects, probably reflecting the importance of a well-tuned diuretic process in hematophagous insects during different moments after the blood meal.
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Affiliation(s)
- Natalia Capriotti
- Laboratorio de Neurobiología de Insectos, Centro Regional de Estudios Genómicos. Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Bvd 120 y 62 (1900), 1900 La Plata, Buenos Aires, Argentina
| | - Juan P Ianowski
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E5
| | - Paula Gioino
- Department of Anatomy, Physiology, and Pharmacology, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E5
| | - Sheila Ons
- Laboratorio de Neurobiología de Insectos, Centro Regional de Estudios Genómicos. Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Bvd 120 y 62 (1900), 1900 La Plata, Buenos Aires, Argentina
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5
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Villalobos-Sambucaro MJ, Diambra LA, Noriega FG, Ronderos JR. Allatostatin-C antagonizes the synergistic myostimulatory effect of allatotropin and serotonin in Rhodnius prolixus (Stal). Gen Comp Endocrinol 2016; 233:1-7. [PMID: 27174746 DOI: 10.1016/j.ygcen.2016.05.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Revised: 05/04/2016] [Accepted: 05/08/2016] [Indexed: 12/26/2022]
Abstract
Haematophagous insects can ingest large quantities of blood in a single meal producing a large quantity of urine in the following hours to eliminate the excess of water and mineral ions incorporated. The excretory activity of the Malpighian tubules is facilitated by an increase in haemolymph circulation as a result of the intensification of aorta contractions, combined with an increase of anterior midgut peristaltic waves. We have recently shown that haemolymph circulation during post-prandial diuresis is modulated by the synergistic activity of allatotropin (AT) and serotonin, resulting in an increase in aorta and crop contraction rates. In the present study we describe the antagonistic effect of allatostatin-C (AST-C) on the increase of aorta frequency of contractions induced by serotonin/AT in Rhodnius prolixus. The administration of AST-C counteracted the increase in the frequency induced by the treatment with serotonin/AT, but did not affect the increase in frequency induced by the administration of serotonin alone, suggesting that AST-C is altering the synergism between serotonin and AT. Furthermore, the administration of AST-C during post-prandial diuresis decreases the number of peristaltic waves of the anterior midgut. The AST-C putative receptor is expressed in the hindgut, midgut and dorsal vessel, three critical organs involved in post-prandial diuresis. All together these findings provide evidence that AST-C plays a key role as a myoregulatory and cardioregulatory peptide in R. prolixus.
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Affiliation(s)
| | | | - Fernando Gabriel Noriega
- Department of Biological Sciences, Florida International University, Miami, FL, USA; Biomolecular Science Institute, Florida International University, Miami, USA
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6
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Petrova A, Moffett DF. Comprehensive Immunolocalization Studies of a Putative Serotonin Receptor from the Alimentary Canal of Aedes aegypti Larvae Suggest Its Diverse Roles in Digestion and Homeostasis. PLoS One 2016; 11:e0146587. [PMID: 26808995 PMCID: PMC4726579 DOI: 10.1371/journal.pone.0146587] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 12/18/2015] [Indexed: 11/17/2022] Open
Abstract
Serotonin regulates key processes including digestion and homeostasis in insects. Serotonin effects are mediated by serotonin receptors that transduce information through initiation of second messenger signaling pathways. Lack of information on serotonin receptors associated with the alimentary canal impedes the understanding of the serotonergic role in insect physiology. To address this void, the present study has cloned and identified a putative serotonin receptor (hereafter AaSeR-1) from the alimentary canal of Aedes aegypti (yellow fever mosquito) larvae. In addition to in-silico analyses of AaSeR-1 primary sequence, immunohistochemical investigations were carried out to elucidate receptor expression patterns. Specific AaSeR-1 immunofluorescence was detected in the caeca, the mid- and hindgut, including the Malpighian tubules. These findings point out not only receptor ubiquitous nature but also its involvement in regulation of different stages of nutrient processing and homeostasis. Furthermore, AaSeR-1 may mediate an array of effects through its differential expression at various cell compartments. While AaSeR-1 specific immunofluorescence was depicted in the nucleus and nucleolus of principal cells of the anterior midgut, in the posterior, analyses suggest receptor association with the plasma membrane of both principal and regenerative cells. In addition, AaSeR-1 immunofluorescence was also found in some enteroendocrine cells and in both circular and longitudinal muscles that innervate the alimentary canal. Overall, immunohistochemical analyses of AaSeR-1 expression indicate that this receptor exercises multiple roles in digestion- and homeostasis-related mechanisms.
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Affiliation(s)
- Adelina Petrova
- School of Biological Sciences, Washington State University, Pullman, WA, United States of America
| | - David Franklin Moffett
- School of Biological Sciences, Washington State University, Pullman, WA, United States of America
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7
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Beyenbach KW, Yu Y, Piermarini PM, Denton J. Targeting renal epithelial channels for the control of insect vectors. Tissue Barriers 2015; 3:e1081861. [PMID: 26716074 DOI: 10.1080/21688370.2015.1081861] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/04/2015] [Accepted: 08/07/2015] [Indexed: 12/14/2022] Open
Abstract
Three small molecules were identified in high throughput screens that 1) block renal inward rectifier potassium (Kir) channels of Aedes aegypti expressed in HEK cells and Xenopus oocytes, 2) inhibit the secretion of KCl but not NaCl in isolated Malpighian tubules, and after injection into the hemolymph, 3) inhibit KCl excretion in vivo, and 4) render mosquitoes flightless or dead within 24h. Some mosquitoes had swollen abdomens at death consistent with renal failure. VU625, the most potent and promising small molecule for development as mosquitocide, inhibits AeKir1-mediated currents with an IC50 less than 100 nM. It is highly selective for AeKir1 over mammalian Kir channels, and it affects only 3 of 68 mammalian membrane proteins. These results document 1) renal failure as a new mode-of-action for mosquitocide development, 2) renal Kir channels as molecular target for inducing renal failure, and 3) the promise of the discovery and development of new species-specific insecticides.
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Affiliation(s)
- Klaus W Beyenbach
- Department of Biomedical Sciences; Cornell University ; Ithaca, NY USA
| | - Yasong Yu
- College of Medicine; SUNY Downstate Medical Center ; Brooklyn, NY USA
| | - Peter M Piermarini
- Department of Entomology; Ohio Agricultural Research and Development Center; The Ohio State University ; Wooster, OH USA
| | - Jerod Denton
- Department of Anesthesiology; Vanderbilt University School of Medicine ; Nashville, TN USA
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8
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Villalobos-Sambucaro MJ, Lorenzo-Figueiras AN, Riccillo FL, Diambra LA, Noriega FG, Ronderos JR. Allatotropin modulates myostimulatory and cardioacceleratory activities in Rhodnius prolixus (Stal). PLoS One 2015; 10:e0124131. [PMID: 25897783 PMCID: PMC4405368 DOI: 10.1371/journal.pone.0124131] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 03/10/2015] [Indexed: 11/22/2022] Open
Abstract
Haematophagous insects can ingest large quantities of blood in a single meal and eliminate high volumes of urine in the next few hours. This rise in diuresis is possible because the excretory activity of the Malpighian tubules is facilitated by an increase in haemolymph circulation as a result of intensification of aorta contractions combined with an increase of the anterior midgut peristaltic waves. It has been previously described that haemolymph circulation during post-prandial diuresis is stimulated by the synergistic activity of allatotropin (AT) and serotonin in the kissing bug Triatoma infestans; resulting in an increase in aorta contractions. In the same species, AT stimulates anterior midgut and rectum muscle contractions to mix urine and feces and facilitate the voiding of the rectum. Furthermore, levels of AT in midgut and Malpighian tubules increased in the afternoon when insects are getting ready for nocturnal feeding. In the present study we describe the synergistic effect of AT and serotonin increasing the frequency of contractions of the aorta in Rhodnius prolixus. The basal frequency of contractions of the aorta in the afternoon is higher that the observed during the morning, suggesting the existence of a daily rhythmic activity. The AT receptor is expressed in the rectum, midgut and dorsal vessel, three critical organs involved in post-prandial diuresis. All together these findings provide evidence that AT plays a role as a myoregulatory and cardioacceleratory peptide in R. prolixus.
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Affiliation(s)
- María José Villalobos-Sambucaro
- Cátedra Histología y Embriología Animal (FCNyM-UNLP), La Plata, Argentina
- Centro Regional de Estudios Genómicos (CREG-UNLP), La Plata, Argentina
| | | | - Fernando Luis Riccillo
- Cátedra Histología y Embriología Animal (FCNyM-UNLP), La Plata, Argentina
- Centro Regional de Estudios Genómicos (CREG-UNLP), La Plata, Argentina
| | | | - Fernando Gabriel Noriega
- Department of Biological Sciences, Florida International University, Miami, Florida, United States of America
| | - Jorge Rafael Ronderos
- Cátedra Histología y Embriología Animal (FCNyM-UNLP), La Plata, Argentina
- Centro Regional de Estudios Genómicos (CREG-UNLP), La Plata, Argentina
- * E-mail:
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9
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Wu Y, Schellinger JN, Huang CL, Rodan AR. Hypotonicity stimulates potassium flux through the WNK-SPAK/OSR1 kinase cascade and the Ncc69 sodium-potassium-2-chloride cotransporter in the Drosophila renal tubule. J Biol Chem 2014; 289:26131-26142. [PMID: 25086033 DOI: 10.1074/jbc.m114.577767] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The ability to osmoregulate is fundamental to life. Adult Drosophila melanogaster maintain hemolymph osmolarity within a narrow range. Osmolarity modulates transepithelial ion and water flux in the Malpighian (renal) tubules of the fly, which are in direct contact with hemolymph in vivo, but the mechanisms causing increased transepithelial flux in response to hypotonicity are unknown. Fly renal tubules secrete a KCl-rich fluid. We have previously demonstrated a requirement for Ncc69, the fly sodium-potassium-2-chloride cotransporter (NKCC), in tubule K(+) secretion. Mammalian NKCCs are regulated by a kinase cascade consisting of the with-no-lysine (WNK) and Ste20-related proline/alanine-rich (SPAK)/oxidative stress response (OSR1) kinases. Here, we show that decreasing Drosophila WNK activity causes a reduction in K(+) flux. Similarly, knocking down the SPAK/OSR1 homolog fray also decreases K(+) flux. We demonstrate that a hierarchical WNK-Fray signaling cascade regulates K(+) flux through Ncc69, because (i) a constitutively active Fray mutant rescues the wnk knockdown phenotype, (ii) Fray directly phosphorylates Ncc69 in vitro, and (iii) the effect of wnk and fray knockdown is abolished in Ncc69 mutants. The stimulatory effect of hypotonicity on K(+) flux is absent in wnk, fray, or Ncc69 mutant tubules, suggesting that the Drosophila WNK-SPAK/OSR1-NKCC cascade is an essential molecular pathway for osmoregulation, through its effect on transepithelial ion flux and fluid generation by the renal tubule.
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Affiliation(s)
- Yipin Wu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8856
| | - Jeffrey N Schellinger
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8856
| | - Chou-Long Huang
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8856
| | - Aylin R Rodan
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8856.
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10
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Hine RM, Rouhier MF, Park ST, Qi Z, Piermarini PM, Beyenbach KW. The excretion of NaCl and KCl loads in mosquitoes. 1. Control data. Am J Physiol Regul Integr Comp Physiol 2014; 307:R837-49. [PMID: 25056103 DOI: 10.1152/ajpregu.00105.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The handling of Na(+) and K(+) loads was investigated in isolated Malpighian tubules and in whole mosquitoes of Aedes aegypti. Isolated Malpighian tubules bathed in Na(+)-rich Ringer solution secreted Na(+)-rich fluid, and tubules bathed in K(+)-rich Ringer solution secreted K(+)-rich fluid. Upon Na(+) loading the hemolymph, the mosquito removed 77% the injected Na(+) within the next 30 min. The rapid onset and magnitude of this diuresis and the excretion of more Na(+) than can be accounted for by tubular secretion in vitro is consistent with the release of the calcitonin-like diuretic hormone in the mosquito to remove the Na(+) load from the hemolymph. Downstream, K(+) was reabsorbed with water in the hindgut, which concentrated Na(+) in excreted urine hyperosmotic to the hemolymph. Upon K(+) loading the hemolymph, the mosquito took 2 h to remove 100% of the injected K(+) from the hemolymph. The excretion of K(+)-rich isosmotic urine was limited to clearing the injected K(+) from the hemolymph with a minimum of Cl(-) and water. As a result, 43.3% of the injected Cl(-) and 48.1% of the injected water were conserved. The cation retained in the hemolymph with Cl(-) was probably N-methyl-d-glucamine, which replaced Na(+) in the hemolymph injection of the K(+) load. Since the tubular secretion of K(+) accounts for the removal of the K(+) load from the hemolymph, the reabsorption of K(+), Na(+), Cl(-), and water must be inhibited in the hindgut. The agents mediating this inhibition are unknown.
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Affiliation(s)
- Rebecca M Hine
- Department of Biomedical Sciences, Cornell University, Ithaca, New York
| | - Matthew F Rouhier
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio; and
| | | | - Zhijun Qi
- Institute of Pesticide Science, Northwestern Agricultural and Forestry University, Yangling, Shaanxi, China
| | - Peter M Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, Ohio; and
| | - Klaus W Beyenbach
- Department of Biomedical Sciences, Cornell University, Ithaca, New York;
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11
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Gioino P, Murray BG, Ianowski JP. Serotonin triggers cAMP and PKA-mediated intracellular calcium waves in Malpighian tubules of Rhodnius prolixus. Am J Physiol Regul Integr Comp Physiol 2014; 307:R828-36. [PMID: 25009218 DOI: 10.1152/ajpregu.00561.2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Rhodnius prolixus is a hematophagous insect vector of Chagas disease capable of ingesting up to 10 times its unfed body weight in blood in a single meal. The excess water and ions ingested with the meal are expelled through a rapid postprandial diuresis driven by the Malpighian tubules. Diuresis is triggered by at least two diuretic hormones, a CRF-related peptide and serotonin, which were traditionally believed to trigger cAMP as an intracellular second messenger. Recently, calcium has been suggested to act as a second messenger in serotonin-stimulated Malpighian tubules. Thus, we tested the role of calcium in serotonin-stimulated Malpighian tubules from R. prolixus. Our results show that serotonin triggers cAMP-mediated intracellular Ca(2+) waves that were blocked by incubation in Ca(2+)-free saline containing the cell membrane-permeant Ca(2+) chelator BAPTA-AM, or the PKA blocker H-89. Treatment with 8-Br-cAMP triggered Ca(2+) waves that were blocked by H-89 and BAPTA-AM. Analysis of the secreted fluid in BAPTA-AM-treated tubules showed a 75% reduction in fluid secretion rate with increased K(+) concentration, reduced Na(+) concentration. Taken together, the results indicate that serotonin triggers cAMP and PKA-mediated Ca(2+) waves that are required for maximal ion transport rate.
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Affiliation(s)
- Paula Gioino
- Department of Physiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Brendan G Murray
- Department of Physiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Juan P Ianowski
- Department of Physiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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12
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Cheng CJ, Baum M, Huang CL. Kidney-specific WNK1 regulates sodium reabsorption and potassium secretion in mouse cortical collecting duct. Am J Physiol Renal Physiol 2012. [PMID: 23195681 DOI: 10.1152/ajprenal.00589.2012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Kidney-specific with-no-lysine kinase 1 (KS-WNK1) is a kinase-deficient variant of WNK1 that is expressed exclusively in the kidney. It is abundantly expressed in the distal convoluted tubule (DCT) and to a lesser extent in the cortical thick ascending limb (cTAL), connecting tubule, and cortical collecting duct (CCD). KS-WNK1 inhibits Na(+)-K(+)-2Cl(-)- and sodium chloride cotransporter-mediated Na(+) reabsorption in cTAL and DCT, respectively. Here, we investigated the role of KS-WNK1 in regulating Na(+) and K(+) transport in CCD using in vitro microperfusion of tubules isolated from KS-WNK1 knockout mice and control wild-type littermates. Because baseline K(+) secretion and Na(+) reabsorption were negligible in mouse CCD, we studied tubules isolated from mice fed a high-K(+) diet for 2 wk. Compared with that in wild-type tubules, K(+) secretion was reduced in KS-WNK1 knockout CCD perfused at a low luminal fluid rate of ~1.5 nl/min. Na(+) reabsorption and the lumen-negative transepithelial potential difference were also lower in the KS-WNK1 knockout CCD compared with control CCD. Increasing the perfusion rate to ~5.5 nl/min stimulated K(+) secretion in the wild-type as well as knockout CCD. The magnitudes of flow-stimulated increase in K(+) secretion were similar in wild-type and knockout CCD. Maxi-K(+) channel inhibitor iberiotoxin had no effect on K(+) secretion when tubules were perfused at ~1.5 nl/min, but completely abrogated the flow-dependent increase in K(+) secretion at ~5.5 nl/min. These findings support the notion that KS-WNK1 stimulates ROMK-mediated K(+) secretion, but not flow-dependent K(+) secretion mediated by maxi-K(+) channels in CCD. In addition, KS-WNK1 plays a role in regulating Na(+) transport in the CCD.
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Affiliation(s)
- Chih-Jen Cheng
- Department of Medicine, Division of Nephrology, UT Southwestern Medical Center, Dallas, TX 75390, USA
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Rodan AR, Baum M, Huang CL. The Drosophila NKCC Ncc69 is required for normal renal tubule function. Am J Physiol Cell Physiol 2012; 303:C883-94. [PMID: 22914641 DOI: 10.1152/ajpcell.00201.2012] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Epithelial ion transport is essential to renal homeostatic function, and it is dysregulated in several diseases, such as hypertension. An understanding of the insect renal (Malpighian) tubule yields insights into conserved epithelial ion transport processes in higher organisms and also has implications for the control of insect infectious disease vectors. Here, we examine the role of the Na(+)-K(+)-2Cl(-) (NKCC) cotransporter Ncc69 in Drosophila tubule function. Ncc69 mutant tubules have decreased rates of fluid secretion and K(+) flux, and these phenotypes were rescued by expression of wild-type Ncc69 in the principal cells of the tubule. Na(+) flux was unaltered in Ncc69 mutants, suggesting Na(+) recycling across the basolateral membrane. In unstimulated tubules, the principal role of the Na(+)-K(+)-ATPase is to generate a favorable electrochemical gradient for Ncc69 activity: while the Na(+)-K(+)-ATPase inhibitor ouabain decreased K(+) flux in wild-type tubules, it had no effect in Ncc69 mutant tubules. However, in the presence of cAMP, which stimulates diuresis, additional Na(+)-K(+)-ATPase-dependent K(+) transport pathways are recruited. In studying the effects of capa-1 on wild-type and Ncc69 mutant tubules, we found a novel antidiuretic role for this hormone that is dependent on intact Ncc69, as it was abolished in Ncc69 mutant tubules. Thus, Ncc69 plays an important role in transepithelial ion and fluid transport in the fly renal tubule and is a target for regulation in antidiuretic states.
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Affiliation(s)
- Aylin R Rodan
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, USA.
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14
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Cheng CJ, Truong T, Baum M, Huang CL. Kidney-specific WNK1 inhibits sodium reabsorption in the cortical thick ascending limb. Am J Physiol Renal Physiol 2012; 303:F667-73. [PMID: 22791335 DOI: 10.1152/ajprenal.00290.2012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Kidney-specific WNK1 (KS-WNK1) is a variant of full-length WNK1. Previous studies have reported that KS-WNK1 is predominantly expressed in the distal convoluted tubule (DCT) where it regulates sodium-chloride cotransporter. The role of KS-WNK1 in other nephron segments is less clear. Here, we measured the expression of KS-WNK1 transcript in microdissected renal tubules and found that KS-WNK1 was most abundant in the DCT, followed by cortical thick ascending limb (cTAL), connecting tubule, and cortical collecting duct. A high K(+) diet enhanced the expression of KS-WNK1 in the DCT and cTAL, selectively. It has been reported that a high-K diet suppresses Na(+) reabsorption in TAL. To understand the role of KS-WNK1 in Na(+) transport in cTAL and the regulation by dietary K(+), we examined Na(+) reabsorption using in vitro microperfusion in cTAL isolated from KS-WNK1-knockout mice and wild-type littermates fed either a control-K(+) or high-K(+) diet. Furosemide-sensitive Na(+) reabsorption in cTAL was higher in KS-WNK1-knockout (KO) mice than in wild-type. A high-K(+) diet inhibited Na(+) reabsorption in cTAL from wild-type mice, but the inhibition was eliminated in KS-WNK1-KO mice. We further examined the role of KS-WNK1 using transgenic mice that overexpress KS-WNK1. Na(+) reabsorption in cTAL was lower in transgenic than in wild-type mice. In whole animal clearance studies, a high-K(+) diet increased daily urine volume and urinary Na(+) and K(+) excretion in wild-type mice, which was blunted in KS-WNK1-KO mice. Thus KS-WNK1 inhibits Na(+) reabsorption in cTAL and mediates the inhibition of Na(+) reabsorption in the segment by a high-K diet.
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Affiliation(s)
- Chih-Jen Cheng
- Division of Nephrology, Department of Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390-8856, USA
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15
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Paluzzi JPV. Anti-diuretic factors in insects: the role of CAPA peptides. Gen Comp Endocrinol 2012; 176:300-8. [PMID: 22226757 DOI: 10.1016/j.ygcen.2011.12.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 12/13/2011] [Accepted: 12/17/2011] [Indexed: 10/14/2022]
Abstract
Insects have adapted to live in a wide variety of habitats and utilize an array of feeding strategies that present challenges to their ability to maintain osmotic balance. Regardless of the feeding strategy, water and ion levels within the haemolymph (insect blood) are maintained within a narrow range. This homeostasis involves the action of a variety of tissues, but is often chiefly regulated by the excretory system. Until recently, most research on the hormonal control of the excretory tissues has focused on factors known to have diuretic activities. In this mini-review, the current state of knowledge on anti-diuretic factors in insects will be discussed with a particular emphasis on the CAPA peptides in the blood-feeding Chagas' disease vector, Rhodnius prolixus.
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Affiliation(s)
- Jean-Paul V Paluzzi
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1.
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Paluzzi JPV, Young P, Defferrari MS, Orchard I, Carlini CR, O'Donnell MJ. Investigation of the potential involvement of eicosanoid metabolites in anti-diuretic hormone signaling in Rhodnius prolixus. Peptides 2012; 34:127-34. [PMID: 22079222 DOI: 10.1016/j.peptides.2011.10.025] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 10/21/2011] [Accepted: 10/23/2011] [Indexed: 11/21/2022]
Abstract
The use of naturally occurring plant-derived compounds for controlling insect pests remains an attractive alternative to potentially dangerous synthetic chemical compounds. One prospective plant-based compound, isoforms of the so-called jack bean urease (JBU) from the jack bean, Canavalia ensiformis, as well a derived peptide, Jaburetox-2Ec, have insecticidal effects on an array of insect species. In the Chagas' disease vector, Rhodnius prolixus, some of the physiological effects attributed to these urease isoforms include inhibition of serotonin (5-HT)-stimulated fluid secretion by the Malpighian tubules (MTs). Here, we investigated whether the effects of these exogenous urease isoforms were targeting the neuroendocrine network involved in the anti-diuretic hormone (RhoprCAPA-2) signaling cascade. We show that pharmacological agents known to interfere with eicosanoid metabolite biosynthesis do not affect RhoprCAPA-2 inhibition of 5-HT-stimulated fluid secretion by MTs. In addition, we demonstrate that RhoprCAPA-2 inhibition of MTs is independent of extracellular or intracellular calcium. Using a heterologous system for analysis of receptor activation, we show that neither JBU nor Jaburetox-2Ec are agonists of the anti-diuretic hormone receptor, RhoprCAPAr1. Finally, activation of the receptor using sub-maximal doses of the natural ligand, RhoprCAPA-2, was not influenced by the presence of either JBU or Jaburetox-2Ec indicating that the urease isoforms do not compete with RhoprCAPA-2 for binding and activation of RhoprCAPAr1. Taken together, these results suggest that at least two distinct mechanisms leading to inhibition of fluid secretion by MTs exist in R. prolixus and, unlike the urease-related effects, the eicosanoid metabolite pathway is not involved in RhoprCAPA-2 mediated anti-diuresis.
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Cheng CJ, Lozano G, Baum M. Prenatal programming of rat cortical collecting tubule sodium transport. Am J Physiol Renal Physiol 2011; 302:F674-8. [PMID: 22189946 DOI: 10.1152/ajprenal.00633.2011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Prenatal insults have been shown to lead to elevated blood pressure in offspring when they are studied as adults. Prenatal administration of dexamethasone and dietary protein deprivation have demonstrated that there is an increase in transporter abundance for a number of nephron segments but not the subunits of the epithelial sodium channel (ENaC) in the cortical collecting duct. Recent studies have shown that aldosterone is elevated in offspring of protein-deprived mothers when studied as adults, but the physiological importance of the increase in serum aldosterone is unknown. As an indirect measure of ENaC activity, we compared the natriuretic response to benzamil in offspring of mothers who ate a low-protein diet (6%) with those who ate a normal diet (20%) for the last half of pregnancy. The natriuretic response to benzamil was greater in the 6% group (821.1 ± 161.0 μmol/24 h) compared with the 20% group (279.1 ± 137.0 μmol/24 h), consistent with greater ENaC activity in vivo (P < 0.05). In this study, we also directly studied cortical collecting tubule function from adult rats using in vitro microperfusion. There was no difference in basal or vasopressin-stimulated osmotic water permeability. However, while cortical collecting ducts of adult offspring whose mothers ate a 20% protein diet had no sodium transport (-1.9 ± 3.1 pmol·mm(-1)·min(-1)), the offspring of rats that ate a 6% protein diet during the last half of pregnancy had a net sodium flux of 10.7 ± 2.6 pmol·mm(-1)·min(-1) (P = 0.01) in tubules perfused in vitro. Sodium transport was measured using ion-selective electrodes, a novel technique allowing measurement of sodium in nanoliter quantities of fluid. Thus we directly demonstrate that there is prenatal programming of cortical collecting duct sodium transport.
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Affiliation(s)
- Chih-Jen Cheng
- Dept. of Pediatrics, U.T. Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9063, USA
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18
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Nguyen H, Donini A. Larvae of the midge Chironomus riparius possess two distinct mechanisms for ionoregulation in response to ion-poor conditions. Am J Physiol Regul Integr Comp Physiol 2010; 299:R762-73. [PMID: 20631293 DOI: 10.1152/ajpregu.00745.2009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined the role of the anal papillae of the freshwater (FW) chironomid larva Chironomus riparius in ionoregulation under ion-poor conditions. The scanning ion-selective electrode technique (SIET) was utilized to characterize the species, direction, and rates of inorganic ion transport by the anal papillae following acute and long-term exposure to ion-poor water (IPW). The major inorganic ions in the hemolymph of larvae treated as above were measured using standard ion-selective microelectrodes. The anal papillae of C. riparius are sites of net NaCl uptake and H(+) secretion under FW and IPW conditions and are not likely to be a major contributor of K(+) exchange. Acute and long-term exposure to IPW increased total net transport of Na(+), Cl(-), and H(+) by the anal papillae, but the mechanisms underlying the increase under the two conditions were different. Acute IPW exposure increased the magnitude of net ion fluxes at sites along the anal papillae, while long-term IPW exposure resulted in increased size of the anal papillae with no change in the magnitude of net ion fluxes. The contribution of the anal papillae to observed alterations of hemolymph ion activities upon exposure to IPW is discussed. Inhibitors of the Na(+)/H(+) exchangers (EIPA) and carbonic anhydrase (methazolamide) provide evidence for Na(+)/H(+) and Cl(-)/HCO(3)(-) exchange mechanisms in the anal papillae. This study demonstrates that C. riparius larvae employ two different mechanisms to upregulate the total net transport of ions by the anal papillae, and these mechanisms are at least partially responsible for regulating hemolymph ion activity.
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Affiliation(s)
- Hang Nguyen
- Department of Biology, York University, Toronto, Ontario, Canada
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19
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Cardioacceleratory and myostimulatory activity of allatotropin in Triatoma infestans. Comp Biochem Physiol A Mol Integr Physiol 2010; 155:371-7. [DOI: 10.1016/j.cbpa.2009.12.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Revised: 11/10/2009] [Accepted: 12/03/2009] [Indexed: 11/23/2022]
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20
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Ianowski JP, Paluzzi JP, Te Brugge VA, Orchard I. The antidiuretic neurohormone RhoprCAPA-2 downregulates fluid transport across the anterior midgut in the blood-feeding insect Rhodnius prolixus. Am J Physiol Regul Integr Comp Physiol 2009; 298:R548-57. [PMID: 20007522 DOI: 10.1152/ajpregu.00208.2009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Osmotic balance in insects is regulated by the excretory system, consisting of Malpighian tubules and the gut under the control of diuretic and antidiuretic factors. Terrestrial insects must conserve water, and antidiuresis is the norm, only interrupted by brief diuretic periods. Surprisingly, little is known about antidiuresis in insects. Two antidiuretic strategies have been described. The first antidiuretic mechanism involves the reabsorption of fluid from the primary urine in the hindgut. More recently, a second antidiuretic strategy was reported, consisting of inhibition of primary urine formation by the Malpighian tubules. Recently, we isolated, characterized, and cloned the gene encoding for the antidiuretic neurohormone (the neuropeptide RhoprCAPA-2) acting on the Malpighian tubules of Rhodnius prolixus. Here we describe a third, novel mechanism central to the antidiuretic strategy of R. prolixus, the inhibition of ion and fluid transport across the anterior midgut by RhoprCAPA-2. Our results show that RhoprCAPA-2 (1 micromol/l) reduces serotonin-stimulated fluid transport from 83 +/- 11 to 12 +/- 12 nl/min and equivalent short-circuit current from 20 +/- 4 to 5 +/- 0.7 microA/cm(2) in diuretic hormone-stimulated anterior midgut. RhoprCAPA-2 appears to function independently of intracellular cGMP or Ca(2+) in the midgut. Thus, the antidiuretic neurohormone RhoprCAPA-2 has multiple target tissues, and we hypothesize that RhoprCAPA-2 functions to coordinate the transport activity of the anterior midgut and Malpighian tubules so that the rate of fluid transport into the haemolymph by the anterior midgut matches the transport rate of Malpighian tubules to maintain the volume and ion composition of haemolymph.
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Affiliation(s)
- Juan P Ianowski
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada.
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21
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Food presentation modifies longevity and the beneficial action of dietary restriction in Drosophila. Exp Gerontol 2009; 45:113-8. [PMID: 19895881 DOI: 10.1016/j.exger.2009.10.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 10/15/2009] [Accepted: 10/29/2009] [Indexed: 11/20/2022]
Abstract
Recent studies have indicated that flies respond to dilute food solutions by compensatory feeding. The existence of compensation mechanisms calls for a reconsideration of the relationships between diet, feeding behaviour and longevity. This study shows that flies fed on liquid diets, sense sucrose and yeast nutrients and adapt to changes in the quantity and presentation of the two nutrients. They have a marked preference for sucrose and regulate their sucrose intake more tightly than their yeast intake. These preferences are not modified as fly age from 1 to 30 days. Compensatory feeding suppresses the beneficial action of dietary restriction on longevity when flies are fed on liquid diets supplemented with yeast extracts. Flies which are given the choice to feed on separate yeast and sucrose food sources were longer lived than flies fed on nutrient mixtures. We conclude that flies sense and respond to specific nutrients and that food presentation is a major factor which determines the sensitivity of flies to dietary restriction.
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Santini MS, Ronderos JR. Daily variation of an allatotropin-like peptide in the Chagas disease vectorTriatoma infestans(klug). BIOL RHYTHM RES 2009. [DOI: 10.1080/09291010802214583] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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23
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Coast GM. Neuroendocrine control of ionic homeostasis in blood-sucking insects. ACTA ACUST UNITED AC 2009; 212:378-86. [PMID: 19151213 DOI: 10.1242/jeb.024109] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The pioneering work of Simon Maddrell established that the rapid postprandial diuresis of the haematophagous insect Rhodnius prolixus is controlled by a diuretic hormone and demonstrated the role of the Malpighian tubules in meeting the volumic, osmotic and ionic challenges posed by an enormous blood meal. A number of diuretic and antidiuretic hormones that control secretion of primary urine by Malpighian tubules have now been identified, but little is known of the interplay between these hormones and those that regulate transport processes in the hindgut. This review therefore focuses on the control of ionic homeostasis in Rhodnius and mosquitoes, because primary urine is voided virtually unchanged during the rapid diuresis that follows a blood meal. At such times, the hindgut has a negligible impact on the volume and composition of the final urine, and neurohormones acting on the Malpighian tubules have a dominant role in the control of ionic homeostasis.
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Affiliation(s)
- Geoffrey M Coast
- Birkbeck College, School of Biological and Chemical Sciences, London, WC1E 7HX UK.
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Stanisçuaski F, Te Brugge V, Carlini CR, Orchard I. Invitro effect of Canavalia ensiformis urease and the derived peptide Jaburetox-2Ec on Rhodnius prolixus Malpighian tubules. JOURNAL OF INSECT PHYSIOLOGY 2009; 55:255-263. [PMID: 19121321 DOI: 10.1016/j.jinsphys.2008.12.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Revised: 12/02/2008] [Accepted: 12/04/2008] [Indexed: 05/27/2023]
Abstract
Ureases are metalloenzymes that are widespread among plants, fungi and bacteria. Urease isoforms (jack bean urease-JBU and canatoxin) from Canavalia ensiformis seeds are toxic to insects and fungi, suggesting a role in plant defense. The entomotoxic effect is due to the release of a 10-kDa peptide by cathepsin-like enzymes in the insect's midgut. Urease causes a decrease in post-feeding weight loss in Rhodnius prolixus, suggesting an effect on water balance. To investigate how this impairment occurs, we have evaluated the action of JBU and the urease-derivated peptide Jaburetox-2Ec on R. prolixus Malpighian tubules and also investigated the involvement of second messengers. JBU and Jaburetox-2Ec affect serotonin-induced secretion from Malpighian tubules. This effect is not cAMP-dependent, but the Jaburetox-2Ec effect is cGMP-dependent. Eicosanoid metabolites and calcium ions appear to be involved in JBU effect on diuresis, but are not involved in the action of Jaburetox-2Ec. Jaburetox-2Ec, but not JBU, causes a change in the transepithelial potential of the tubules. Canatoxin has a similar effect on tubules secretion, decreasing the secretion rate, but the urease from Helicobacter pylori has no significant effect. These data are helpful in our understanding of the actions of ureases and derived peptides on insects, and also reinforces the potential use of these proteins as biopesticides.
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Affiliation(s)
- Fernanda Stanisçuaski
- Department of Biophysics, Institute of Biosciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, 91501-970, Brazil.
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25
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O'Donnell MJ. Too much of a good thing: how insects cope with excess ions or toxins in the diet. J Exp Biol 2009; 212:363-72. [DOI: 10.1242/jeb.023739] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
SUMMARYMuch of our understanding of the ionoregulatory and excretory physiology of blood-feeding insects can be traced to a series of papers by Simon Maddrell and colleagues in the 1970s and 1980s. These studies of the Malpighian (renal)tubules of Rhodnius prolixus revealed a number of physiological adaptations to the short-term and long-term stresses associated with blood feeding. More recent electrophysiological studies using voltage- and ion-selective microelectrodes have extended our understanding of the mechanisms and control of ion transport by the secretory and reabsorptive segments of the Rhodnius Malpighian tubule. The discovery that the rates of transport of organic anions, urates and Ca2+ are synchronized to coincide with the appearance of the products of blood meal digestion in the haemolymph of Rhodnius has stimulated parallel studies in Drosophila. This recent research has examined how excretory mechanisms for organic cations and organic anions are altered by exposure to such compounds in the diet. These studies also show that the Drosophila Malpighian tubule provides a useful model for analysis of the roles of transporters such as P-glycoproteins and multidrug resistance-associated proteins in the excretion of toxins.
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Affiliation(s)
- M. J. O'Donnell
- Department of Biology, McMaster University, 1280 Main Street West,Hamilton, Ontario, Canada L8S 4K1
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Santini MS, Ronderos JR. Allatotropin-like peptide in Malpighian tubules: insect renal tubules as an autonomous endocrine organ. Gen Comp Endocrinol 2009; 160:243-9. [PMID: 19118556 DOI: 10.1016/j.ygcen.2008.12.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Revised: 10/13/2008] [Accepted: 12/02/2008] [Indexed: 11/23/2022]
Abstract
Malpighian tubules (MTs) are recognised as the main excretory organ in insects, ensuring water and mineral balance. Haematophagous insects incorporate with each meal a large quantity of blood, producing a particularly large volume of urine in a few hours. In the present study, we report the presence of an allatotropin-like (AT-like) peptide in MTs of Triatoma infestans (Klug). The AT-like content in MTs decreased during the first hours after blood-intake, correlating with the post-prandial diuresis. In vivo artificial dilution of haemolymph showed a similar effect. Isolated MTs challenged with a diluted saline solution resulted in an autonomous and reversible response of the organ regulating the quantity of peptide released to the medium, and suggesting that MTs synthesise the AT-like peptide. While MTs are recognised as the target for several hormones, our results corroborate that they also have the ability to produce and secrete a hormone in an autonomous way.
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Affiliation(s)
- Maria Soledad Santini
- Centro Regional de Estudios Genomicos (CREG), Universidad Nacional de La Plata, Parque Tecnologico Florencio Varela, Buenos Aires, Argentina
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Gonzalez R, Orchard I. Physiological activity of neuropeptide f on the hindgut of the blood-feeding hemipteran, Rhodnius prolixus. JOURNAL OF INSECT SCIENCE (ONLINE) 2009; 9:1-14. [PMID: 20050776 PMCID: PMC3011914 DOI: 10.1673/031.009.5701] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 08/17/2008] [Indexed: 05/28/2023]
Abstract
Current hypotheses propose that, in the invertebrates, neuropeptide F (NPF), the vertebrate NPY homologue, may be capable of regulating responses to diverse cues related to nutritional status and feeding. An investigation into the effects of Drosophila melanogaster NPF (DrmNPF) and Anopheles gambiae NPF (AngNPF) on hindgut physiology of Rhodnius prolixus Stal (Heimptera: Reduviidae) suggests a myoinhibitory role for these peptides and the R. prolixus native peptide. Extracts of the central nervous system of R. prolixus were processed and several HPLC-fractions revealed NPF-like activity within the nanomolar equivalent range when tested using the hindgut contraction assay. Although NPF has been shown to decrease epithelial membrane potential in Aedes aegypti larval midgut preparations, NPF does not appear to play a role in epithelial transport of potassium in the hindgut. While the function of NPF has yet to be established, NPF-like effects suggest multiple physiological roles for NPF among invertebrates.
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Affiliation(s)
- Ronald Gonzalez
- Department of Biology, York University, 4700 Keele St., Toronto, ON, Canada M3J IP3
| | - Ian Orchard
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Rd, Mississauga, ON, L5L 1C6
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Donini A, O'Donnell MJ, Orchard I. Differential actions of diuretic factors on the Malpighian tubules of Rhodnius prolixus. ACTA ACUST UNITED AC 2008; 211:42-8. [PMID: 18083731 DOI: 10.1242/jeb.011882] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effects of corticotropin-releasing factor (CRF)-related (ZooneDH), calcitonin (CT)-related (RhoprDH(31)) and kinin-related (leucokinin I) peptides on the ion composition of fluid secreted by upper Rhodnius prolixus Malpighian tubules and on KCl reabsorption by the lower tubules were assessed. ZooneDH stimulated fluid secretion while increasing the [Na(+)] of secreted fluid at the expense of [K(+)]. Upper tubules responded to ZooneDH with a characteristic triphasic change in the transepithelial potential (TEP), reminiscent of the response to 5-hydroxytryptamine (5HT). RhoprDH(31) produced a small (~9 mV) lumen-positive shift in TEP of the upper tubule but had no effect on the rate of fluid secretion or ion composition of the secreted fluid. In contrast to 5HT, both peptides failed to activate KCl reabsorption by the lower tubule. Leucokinin I had no effect on the ion composition of fluid secreted by whole or upper Malpighian tubules. We propose that: (1) 5HT and a native CRF-related peptide similar to ZooneDH activate the same second messenger systems and ion transporters in the upper tubule cells; (2) CRF-related peptide is utilized to maintain high rates of fluid secretion during the post-feeding diuresis and is additionally used at times when KCl reabsorption is unnecessary or detrimental. The differential actions of multiple diuretic factors allows for intricate control of ionic and osmotic balance in R. prolixus.
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Affiliation(s)
- Andrew Donini
- Department of Biology, York University, Toronto, Ontario, Canada.
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29
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Balczun C, Knorr E, Topal H, Meiser CK, Kollien AH, Schaub GA. Sequence characterization of an unusual lysozyme gene expressed in the intestinal tract of the reduviid bug Triatoma infestans (Insecta). Parasitol Res 2007; 102:229-32. [PMID: 17899195 DOI: 10.1007/s00436-007-0751-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2007] [Accepted: 08/30/2007] [Indexed: 10/22/2022]
Abstract
Antibacterial proteins like lysozyme are important components of the insect non-specific immune response against bacteria. The complementary deoxyribonucleic acid (cDNA) encoding a new lysozyme from Triatoma infestans, named lysozyme2, has been amplified by polymerase chain reaction and the rapid amplification of cDNA ends technique. The gene is expressed in the small intestine of the insect. The deduced protein sequence shows up to 70% similarity to lysozymes from other species. Furthermore, the protein exhibits significant structural concordance to other insect lysozymes. A striking feature of the lysozyme2 protein is the replacement of the conserved amino acid residues of the active site of classical c-type lysozymes, glutamate and aspartate, by valine and tyrosine.
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Affiliation(s)
- C Balczun
- Zoology/Parasitology Group, Ruhr-University, 44780, Bochum, Germany
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30
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Santini MS, Ronderos JR. Allatotropin-like peptide released by Malpighian tubules induces hindgut activity associated with diuresis in the Chagas disease vector Triatoma infestans (Klug). J Exp Biol 2007; 210:1986-91. [PMID: 17515423 DOI: 10.1242/jeb.004291] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
SUMMARY
Haematophagous insects incorporate a large amount of blood with each meal,producing a big quantity of urine in a few hours to eliminate the excess water and Na+. Malpighian tubules (MTs) have traditionally been seen as a system that responds to neuroendocrine stimulus. In a related paper, we demonstrated that MTs of Triatoma infestans produce an autonomous endocrine secretion of an allatotropin-like (AT-like) peptide. In the present study, we report a myostimulatory activity of AT at the level of the hindgut(HG), associated with endocrine mechanisms regulating post-prandial diuresis. Allatotropin induced an increase in frequency and intensity of peristaltic contractions at the level of the HG. The release of the HG content in MTs–HG in vitro preparations undergoing an osmotic shock occurred at different times, depending on the number of MTs present, and there was no release in treatments without MTs. The application of an AT-antiserum to MTs–HG preparations undergoing osmotic shock produced a delay or a long-term blockade of diuresis, depending on the antiserum dilution applied. Similar results were obtained when AT-antiserum was applied in vivoprior to blood intake, decreasing the volume of urine eliminated during the first 2 h. Our results allow us to assign a specific endocrine function to the AT-like peptide released by MTs that is linked to the elimination of urine after blood meals.
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Affiliation(s)
- Maria Soledad Santini
- Centro Regional de Estudios Genomicos (CREG-UNLP) and Catedra Histol, Embriol, Animal (FCNyM-UNLP), La Plata, Argentina
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31
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Coast G. The endocrine control of salt balance in insects. Gen Comp Endocrinol 2007; 152:332-8. [PMID: 17400222 DOI: 10.1016/j.ygcen.2007.02.018] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Revised: 02/12/2007] [Accepted: 02/17/2007] [Indexed: 11/20/2022]
Abstract
An overview is given of the role of Malpighian (renal) tubules and the hindgut (ileum and rectum) in the excretory process of insects. The review focuses on the mechanism of primary urine production by Malpighian tubules and its control by neurohormones, which includes serotonin and neuropeptides resembling mammalian corticotropin-releasing factor (CRF) and calcitonin. Particular emphasis is given to in vitro studies of the effect of neurohormones on Malpighian tubule ion transport and a consideration of their likely role in the regulation of salt balance in vivo.
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Affiliation(s)
- Geoffrey Coast
- School of Biological & Chemical Sciences, Birkbeck (University of London), Malet Street, London WC1E 7HX, UK.
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32
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Ianowski JP, O'Donnell MJ. Electrochemical gradients for Na+, K+,Cl– and H+ across the apical membrane in Malpighian (renal) tubule cells ofRhodnius prolixus. J Exp Biol 2006; 209:1964-75. [PMID: 16651561 DOI: 10.1242/jeb.02210] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
SUMMARYMeasurements of intracellular and luminal ion activities as well as membrane potential were used to calculate electrochemical gradients for Cl–, Na+, K+ and H+ across the apical membrane during fluid secretion by Malpighian tubules of Rhodnius prolixus. The results show that the contribution of Na+/H+ and/or K+/H+ exchangers to fluid secretion is feasible both in unstimulated and serotonin-stimulated tubules. Similarly, the electrochemical potential for Cl– is consistent with the passive movement of Cl– from cell to lumen through Cl– channels. The contribution of apical K+:Cl– cotransport and/or paracellular Cl– movement to net transepithelial ion transport is thermodynamically unfeasible. pH in the lumen (pH 6.08±0.1, N=6) was more acid than in the bath (pH 7.25±0.01, N=26) and serotonin stimulation produced a significant increase in lumen pH to 6.32±0.04 (N=5). Intracellular pH was 6.97±0.01 and 6.82±0.04 in unstimulated and serotonin-stimulated tubules, respectively. Lumen pH was altered whereas intracellular pH was tightly regulated during serotonin and bumetanide treatment. Furthermore, DIDS or amiloride treatment did not affect intracellular pH. However, intracellular pH shifted 0.25 pH units more acid in Na+-free saline, suggesting that a Na+-dependent pH regulatory mechanism is at play in steady state pH regulation during fluid secretion by Malpighian tubules of Rhodnius prolixus. The data are consistent with a role for a basolateral Na+/H+ exchanger in intracellular pH regulation during fluid secretion.
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Affiliation(s)
- Juan P Ianowski
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada.
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33
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Litwiller SL, O'Donnell MJ, Wright PA. Rapid increase in the partial pressure of NH3 on the cutaneous surface of air-exposed mangrove killifish,Rivulus marmoratus. J Exp Biol 2006; 209:1737-45. [PMID: 16621954 DOI: 10.1242/jeb.02197] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYMangrove killifish, Rivulus marmoratus, are tolerant of prolonged periods of air exposure (>30 days). Air-exposed R. marmoratuseliminate more than 40% of their total ammonia through NH3volatilization; however, the sites and mechanisms are unclear. We hypothesized that the cutaneous surface is an important site of NH3volatilization in air-exposed R. marmoratus. Ion-selective microelectrodes were used to measure the NH4+concentration and pH in the boundary layer on the cutaneous surface of fish in water or air (acute: 1 h, chronic: 11 days). Following acute and chronic air exposure, there was a ∼18-fold increase in the NH4+concentration and a 0.3–0.6 pH unit increase on the cutaneous surface of R. marmoratus. In air-exposed fish, the calculated cutaneous partial pressure (PNH3) was 608–1251 μTorr,representing a 33- to 75-fold increase over control (immersed) fish. The PNH3 on the cutaneous surface water film was more than sufficient to account for the rate of NH3 volatilization under terrestrial conditions. Together, these data indicate that during air exposure, R. marmoratus utilize the cutaneous surface as a key site of NH3 volatilization.
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Affiliation(s)
- S L Litwiller
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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Ianowski JP, Christensen RJ, O'Donnell MJ. Na+ competes with K+ in bumetanide-sensitive transport by Malpighian tubules ofRhodnius prolixus. J Exp Biol 2004; 207:3707-16. [PMID: 15371478 DOI: 10.1242/jeb.01203] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYWe examined the effects of bathing saline Na+/K+ratio, bumetanide and hydrochlorothiazide on fluid and ion transport by serotonin-stimulated Malpighian tubules of Rhodnius prolixus. Previous pharmacological and electrophysiological studies indicate that a bumetanide-sensitive Na+/K+/2Cl–cotransporter is the primary route for basolateral ion entry into the cell during fluid secretion. The goal of this study was to resolve the apparent conflict between relatively high secretion rates by tubules bathed in K+-free saline and the evidence that Na+/K+/2Cl– cotransporters described in other systems have an absolute requirement for all three ions for translocation. Our measurements of fluid secretion rate, ion fluxes and electrophysiological responses to serotonin show that fluid secretion in K+-free saline is bumetanide sensitive and hydrochlorothiazide insensitive. Dose–response curves of secretion rate versusbumetanide concentration were identical for tubules bathed in K+-free and control saline with IC50 values of 2.6×10–6 mmol l–1 and 2.9×10–6 mmol l–1, respectively. Double-reciprocal plots of K+ flux versus bathing saline K+ concentration showed that increasing Na+concentration in the bathing fluid increased Kt but had no effect on Jmax, consistent with competitive inhibition of K+ transport by Na+. We propose that the competition between Na+ and K+ for transport by the bumetanide-sensitive transporter is part of an autonomous mechanism by which Malpighian tubules regulate haemolymph K+ concentration.
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Affiliation(s)
- Juan P Ianowski
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada, L8S 4K1
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35
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Ianowski JP, O'Donnell MJ. Basolateral ion transport mechanisms during fluid secretion byDrosophilaMalpighian tubules: Na+ recycling,Na+:K+:2Cl– cotransport and Cl– conductance. J Exp Biol 2004; 207:2599-609. [PMID: 15201292 DOI: 10.1242/jeb.01058] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYMechanisms of ion transport during primary urine formation by the Malpighian tubule of Drosophila melanogaster were analyzed through measurements of fluid secretion rate, transepithelial ion flux, basolateral membrane potential (Vbl) and intracellular activities of K+ (aKi) and Cl–(aCli). Calculation of the electrochemical potentials for both ions permitted assessment of the possible contributions of K+ channels, Na+:K+:2Cl–cotransport, and K+:Cl– cotransport, to net transepithelial ion secretion across the basolateral membrane. The data show that passive movement of both K+ and Cl– from cell to bath is favoured across the basolateral membrane, indicating that both ions are actively transported into the cell. Contributions of basolateral K+ channels or K+:Cl– cotransporters to net transepithelial ion secretion can be ruled out. After prior exposure of tubules to ouabain, subsequent addition of bumetanide reduced fluid secretion rate, K+ flux and Na+ flux, indicating a role for a Na+:K+:2Cl– cotransporter in fluid secretion. Addition of the K+ channel blocker Ba2+ had no effect on aKi or aCli. Addition of Ba2+ unmasked a basolateral Cl– conductance and the hyperpolarization of Vbl in response to Ba2+ was Cl–-dependent. A new model for fluid secretion proposes that K+ and Cl– cross the basolateral membrane through a Na+-driven Na+:K+:2Cl–cotransporter and that most of the Na+ that enters the cells is returned to the bath through the Na+/K+-ATPase.
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Affiliation(s)
- Juan P Ianowski
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada, L8S 4K1
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Abstract
We have studied Malpighian tubules of Aedes aegypti using a variety of methods: Ramsay fluid secretion assay, electron probe analysis of secreted fluid, in vitro microperfusion and two-electrode voltage clamp. Collectively, these methods have allowed us to elucidate transepithelial transport mechanisms under control conditions and in the presence of diuretic peptides. Mosquito natriuretic peptide (MNP), a corticotropin-releasing factor (CRF)-like diuretic peptide, selectively increases transepithelial secretion of NaCl and water, meeting the NaCl loads of the blood meal. The intracellular messenger of MNP is cAMP, which increases the Na+ conductance and activates the Na+/K+/2Cl- -cotransporter in the basolateral membrane of principal cells. Leucokinin non-selectively increases transepithelial NaCl and KCl secretion, which may deal with hemolymph volume expansions or reduce the flight pay load upon eclosion from the aquatic habitat. The non-selective NaCl and KCl diuresis stems from the increase in septate junctional Cl- conductance activated by leucokinin using Ca2+ as second messenger. Fundamental to diuretic mechanisms are powerful epithelial transport mechanisms in the distal segment of the Malpighian tubules, where transepithelial secretion rates can exceed the capacity of mammalian glomerular kidneys in the renal turnover of the extracellular fluid compartment. In conjunction with powerful epithelial transport mechanisms driven by the V-type H+-ATPase, diuretic hormones enable hematophagous and probably also phytophagous insects to deal with enormous dietary loads, thereby contributing to the evolutionary success of insects.
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Affiliation(s)
- Klaus W Beyenbach
- Department of Biomedical Sciences, VRT 8004, Cornell University, Ithaca, NY 14853, USA.
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37
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O'Donnell MJ, Ianowski JP, Linton SM, Rheault MR. Inorganic and organic anion transport by insect renal epithelia. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2003; 1618:194-206. [PMID: 14729156 DOI: 10.1016/j.bbamem.2003.07.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Insect renal organs typically exhibit high rates of transport of inorganic and organic anions, and therefore provide useful models for the study of epithelial anion transport and its control. Isolated Malpighian tubules of some species secrete a volume of iso-osmotic fluid equal to their own volume in 10-15 s, which means that cellular Cl(-) content is exchanged every 3-5 s. Anion transport can also be achieved against extreme thermodynamic gradients. The concentration of K(+) and Cl(-) in the lumen of the Malpighian tubules of some desert beetles approaches or exceeds saturation. A basolateral Na(+):K(+):2Cl(-) cotransporter plays an important role in vectorial ion transport in Malpighian tubules of many species, but there is also evidence for coupling of Cl(-) transport to the movement of a single cationic species (Na(+) or K(+)). Although an apical vacuolar H(+)-ATPase plays a primary role in energizing transepithelial secretion of chloride via channels or cotransporters in the secretory segment of the Malpighian tubule, several different ATPases have been implicated in reabsorption of Cl(-) by the lower Malpighian tubule or hindgut. Chloride transport is known to be controlled by several neuropeptides, amines and intracellular second messengers. Insect renal epithelia are also important in excretion of potentially toxic organic anions, and the transporters involved may play a role in resistance to insecticides of natural or anthropogenic origin.
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Affiliation(s)
- Michael J O'Donnell
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1.
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Hazel MH, Ianowski JP, Christensen RJ, Maddrell SHP, O'Donnell MJ. Amino acids modulate ion transport and fluid secretion by insect Malpighian tubules. J Exp Biol 2003; 206:79-91. [PMID: 12456699 DOI: 10.1242/jeb.00058] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Insect haemolymph typically contains very high levels of free amino acids. This study shows that amino acids can modulate the secretion of ions and water by isolated Malpighian tubules of Rhodnius prolixus and Drosophila melanogaster. Secretion rates of Rhodnius tubules in amino-acid-free saline increase after addition of serotonin to a peak value, then slowly decline to a plateau. Addition of glutamine, glutamate or aspartate to such tubules increases secretion rates dramatically relative to the controls in amino-acid-free saline, and these increases are sustained for 1-2 h. Seven other amino acids have more modest stimulatory effects, whereas lysine and arginine are inhibitory. Secreted fluid pH and Na(+) concentration increase and K(+) concentration decreases in response to glutamine. Pre-incubation of unstimulated tubules in saline solutions containing amino acids followed by stimulation with serotonin in amino-acid-free saline shows that the effects of amino acids far outlast the duration of exposure to them. Amino acids do not appear to be important as metabolites in Rhodnius tubules, nor do they act to draw significant amounts of water into the lumen by osmosis. Significant stimulation of fluid secretion can be achieved by physiological levels of particular amino acids, whereas those amino acids that inhibit fluid secretion only do so at concentrations much above those at which they occur naturally in the haemolymph. Secretion rates of unstimulated or stimulated Drosophila tubules are increased by pre-incubation in saline solutions containing glutamine or methionine or by continuous exposure to glutamine, methionine or tyrosine. Cysteine dramatically inhibited fluid secretion by Drosophila tubules, but only at concentrations well above the physiological range. We suggest that the amino acids probably function as compatible intracellular osmolytes that are necessary for sustained secretion at high rates by the Malpighian tubules.
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Affiliation(s)
- Matthew H Hazel
- Dept of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4KI, Canada
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Ianowski JP, Christensen RJ, O'Donnell MJ. Intracellular ion activities in Malpighian tubule cells ofRhodnius prolixus: evaluation of Na+-K+-2Cl-cotransport across the basolateral membrane. J Exp Biol 2002; 205:1645-55. [PMID: 12000809 DOI: 10.1242/jeb.205.11.1645] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYIntracellular ion activities (aion) and basolateral membrane potential (Vbl) were measured in Malpighian tubule cells of Rhodnius prolixus using double-barrelled ion-selective microelectrodes. In saline containing 103mmoll-1Na+, 6mmoll-1 K+ and 93mmoll-1Cl-, intracellular ion activities in unstimulated upper Malpighian tubules were 21, 86 and 32mmoll-1, respectively. In serotonin-stimulated tubules, aCl was unchanged, whereas aNa increased to 33mmoll-1 and aK declined to 71mmoll-1. Vbl was -59mV and -63mV for unstimulated and stimulated tubules, respectively. Calculated electrochemical potentials(Δμ/F) favour passive movement of Na+ into the cell and passive movement of Cl- out of the cell in both unstimulated and serotonin-stimulated tubules. Passive movement of K+ out of the cell is favoured in unstimulated tubules. In stimulated tubules, Δμ/F for K+ is close to 0 mV.The thermodynamic feasibilities of Na+-K+-2Cl-, Na+-Cl-and K+-Cl- cotransporters were evaluated by calculating the net electrochemical potential (Δμnet/F) for each transporter. Our results show that a Na+-K+-2Cl- or a Na+-Cl- cotransporter but not a K+-Cl- cotransporter would permit the movement of ions into the cell in stimulated tubules. The effects of Ba2+ and ouabain on Vbl and rates of fluid and ion secretion show that net entry of K+ through ion channels or the Na+/K+-ATPase can be ruled out in stimulated tubules. Maintenance of intracellular Cl- activity was dependent upon the presence of both Na+ and K+ in the bathing saline. Bumetanide reduced the fluxes of both Na+ and K+. Taken together, the results support the involvement of a basolateral Na+-K+-2Cl- cotransporter in serotonin-stimulated fluid secretion by Rhodnius prolixus Malpighian tubules.
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Affiliation(s)
- Juan P Ianowski
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1.
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Dube K, McDonald DG, O'Donnell MJ. Calcium transport by isolated anterior and posterior Malpighian tubules of Drosophila melanogaster: roles of sequestration and secretion. JOURNAL OF INSECT PHYSIOLOGY 2000; 46:1449-1460. [PMID: 10891573 DOI: 10.1016/s0022-1910(00)00069-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Ca(2+) transport was examined in isolated Malpighian tubules (MTs) of adult Drosophila melanogaster. All segments of both anterior and posterior MTs have substantial capacity to transport Ca(2+) and to play a role, therefore, in calcium homeostasis and elimination of excess dietary Ca(2+). Approximately 85% of Ca(2+) which enters the tubule is sequestered, and approximately 15% is secreted in soluble form into the tubule lumen. Tubules secreting fluid at maximal rates can remove an amount of Ca(2+) equal to the whole animal calcium content in approximately 9 h. Distal segments of the pair of anterior MTs can sequester the same amount of Ca(2+) in <2 h. Functional advantages of high Ca(2+) turnover rates are discussed. Transepithelial Ca(2+) secretion is increased by treatments which depolarize the transepithelial potential (thapsigargin, high K(+)), or acidify the secreted fluids (bicarbonate-free salines). The effects of pharmacological reagents and variations in bathing saline ionic composition indicate that the processes of secretion and sequestration are controlled independently, and that diltiazem-sensitive Ca(2+) channels are an important component of sequestration. The contribution of some form of apical Ca(2+) pump is evaluated.
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Affiliation(s)
- K Dube
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, L8S 4K1, Ontario, Canada
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41
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Dube KA, McDonald DG, O'Donnell MJ. Calcium homeostasis in larval and adult Drosophila melanogaster. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2000; 44:27-39. [PMID: 10790183 DOI: 10.1002/(sici)1520-6327(200005)44:1<27::aid-arch4>3.0.co;2-i] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Calcium homeostasis in Drosophila melanogaster was examined in response to the challenges imposed by growth, reproduction and variations in dietary calcium content. Turnover time for calcium, calculated as the time for (45)Ca(2+)to accumulate to half the steady state value of 3.46 nmol/fly, was 3.3 days. Although larvae weighed 2x as much as adults, they contained 3-4x as much calcium. Anterior Malpighian tubules (Mts) contain much more calcium than posterior Mts, accounting for 25-30% of the calcium content of the whole fly. In response to a 6.2-fold increase in dietary calcium level, calcium content of whole flies increased only 10%. Hemolymph calcium concentration ( approximately 0.5 mM) was similar in males and females and in animals raised on diets differing in calcium content. Fluid secretion rate, secreted fluid calcium concentration, and transepithelial calcium flux in tubules isolated from flies raised on high and low calcium diets did not differ significantly. Malpighian tubules secrete calcium at rates sufficient to eliminate whole body calcium content in 0.5 and 3 days for tubules secreting fluid at basal and maximal rates, respectively. It is suggested that flies absorb high quantities of calcium from the diet and maintain homeostasis through the combined effects of elimination of calcium in fluid secreted by the Malpighian tubules and the sequestration of calcium in granules, especially within the distal segment of the anterior pair of Malpighian tubules.
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Affiliation(s)
- K A Dube
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
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42
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O'Donnell MJ, Spring JH. Modes of control of insect Malpighian tubules: synergism, antagonism, cooperation and autonomous regulation. JOURNAL OF INSECT PHYSIOLOGY 2000; 46:107-117. [PMID: 12770242 DOI: 10.1016/s0022-1910(99)00119-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Rates of fluid and ion secretion by insect Malpighian tubules are controlled by peptides, including CRF-related peptides and kinins, and in some species by serotonin. It now appears to be a general rule that tubule secretion rate is controlled through the interaction of two or more haemolymph-borne factors. In this review we suggest that these interactions may be classified as synergistic, cooperative, or antagonistic. When presented together, two diuretic factors may act in synergism, so that fluid secretion is stimulated to a greater extent than the sum of their individual effects. Synergism may involve one or more second messenger systems. Alternatively, diuretic factors may act in cooperation, so that although their overall effects are additive, cation and anion transport pathways are controlled separately by distinct second messenger systems. There is also one example of antagonism between factors controlling tubule secretion and between their respective second messengers; one factor is stimulatory, the other is inhibitory. In addition to the complex control of fluid and ion transport by haemolymph-borne factors, sophisticated autonomous regulatory mechanisms have been identified in Malpighian tubules. When triggered by appropriate stimuli, these mechanisms play homeostatic roles, preserving haemolymph osmolality or ionic composition.
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Affiliation(s)
- M J. O'Donnell
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Canada
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Linton SM, O'Donnell MJ. Contributions of K+:Cl- cotransport and Na+/K+-ATPase to basolateral ion transport in malpighian tubules of Drosophila melanogaster. J Exp Biol 1999; 202:1561-70. [PMID: 10229702 DOI: 10.1242/jeb.202.11.1561] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mechanisms of Na+ and K+ transport across the basolateral membrane of isolated Malpighian tubules of Drosophila melanogaster were studied by examining the effects of ion substitution and putative inhibitors of specific ion transporters on fluid secretion rates, basolateral membrane potential and secreted fluid cation composition. Inhibition of fluid secretion by [(dihydroindenyl)oxy]alkanoic acid (DIOA) and bumetanide (10(-)4 mol l-1) suggested that a K+:Cl- cotransporter is the main route for K+ entry into the principal cells of the tubules. Differences in the effects of bumetanide on fluxes of K+ and Na+ are inconsistent with effects upon a basolateral Na+:K+:2Cl- cotransporter. Large differences in electrical potential across apical (>100 mV, lumen positive) and basolateral (<60 mV, cell negative) cell membranes suggest that a favourable electrochemical gradient for Cl- entry into the cell may be used to drive K+ into the cell against its electrochemical gradient, via a DIOA-sensitive K+:Cl- cotransporter. A Na+/K+-ATPase was also present in the basolateral membrane of the Malpighian tubules. Addition of 10(-)5 to 10(-)3 mol l-1 ouabain to unstimulated tubules depolarized the basolateral potential, increased the Na+ concentration of the secreted fluid by 50-73 % and increased the fluid secretion rate by 10-19 %, consistent with an increased availability of intracellular Na+. We suggest that an apical vacuolar-type H+-ATPase and a basolateral Na+/K+-ATPase are both stimulated by cyclic AMP. In cyclic-AMP-stimulated tubules, K+ entry is stimulated by the increase in the apical membrane potential, which drives K+:Cl- cotransport at a faster rate, and by the stimulation of the Na+/K+-ATPase. Fluid secretion by cyclic-AMP-stimulated tubules was reduced by 26 % in the presence of ouabain, suggesting that the Na+/K+-ATPase plays a minor role in K+ entry into the tubule cells. Malpighian tubules secreted a Na+-rich (150 mmol l-1) fluid at high rates when bathed in K+-free amino-acid-replete saline (AARS). Secretion in K+-free AARS was inhibited by amiloride and bafilomycin A1, but not by bumetanide or hydrochlorothiazide, which inhibit Na+:Cl- cotransport. There was no evidence for a Na+ conductance in the basolateral membrane of unstimulated or cyclic-AMP-stimulated tubules. Possible mechanisms of Na+ entry into the tubule cells include cotransport with organic solutes such as amino acids and glucose.
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Affiliation(s)
- S M Linton
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.
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O'Donnell MJ, Quinlan MC. Anti-diuresis in the blood-feeding insect Rhodnius prolixus Stål: antagonistic actions of cAMP and cGMP and the role of organic acid transport. JOURNAL OF INSECT PHYSIOLOGY 1998; 44:561-568. [PMID: 12769938 DOI: 10.1016/s0022-1910(98)00047-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Secretion of primary urine by upper Malpighian tubules of the blood-sucking insect Rhodnius prolixus has recently been shown to be inhibited by cyclic GMP (cGMP). In the present work, we have demonstrated that cGMP has effects antagonistic to those of cAMP in Rhodnius tubules and have further characterized the effects of cGMP on tubular secretion. Cyclic GMP inhibited secretion at all concentrations from 5x10(-6) to 10(-3)M, though this inhibition was partially or wholly reversed by large (2mM) doses of cAMP. While sub-maximal concentrations of cGMP did not significantly alter [K(+)] and [Na(+)] of secreted fluid, high external [cGMP] reduced secretion to minimal levels and caused [K(+)] and [Na(+)] to approach pre-stimulation levels. Cyclic GMP does not appear to affect the permeability of the lower Malpighian tubule to water. Both cAMP and cGMP likely enter tubule cells by way of an organic acid transporter whose activity is induced by feeding. Sensitivity of the tubules to exogenous cGMP and cAMP, which is assumed to be a function of transport activity, reaches a peak approximately 5 days after the blood meal and declines rapidly thereafter. Transport of anions into upper tubules involves at least two different transporters: one for acylamides (e.g., p-aminohippuric acid) and another for sulphonates (e.g., amaranth, phenol red). Amaranth and phenol red blocked the actions of both cGMP and cAMP, whereas p-aminohippuric acid was without effect. This suggests that cyclic nucleotides enter by way of the sulphonate transporter.
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Affiliation(s)
- M J. O'Donnell
- Department of Biology, McMaster University, Hamilton, Canada
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O'Donnell MJ, Fletcher M, Haley CA. KCl reabsorption by the lower malpighian tubule of rhodnius prolixus: inhibition by Cl(-) channel blockers and acetazolamide. JOURNAL OF INSECT PHYSIOLOGY 1997; 43:657-665. [PMID: 12769977 DOI: 10.1016/s0022-1910(97)00019-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Iono- and osmoregulation by the blood-feeding hemipteran Rhodnius prolixus involves co-ordinated actions of the upper and lower Malpighian tubules. The upper tubule secretes ions (Na(+), K(+), Cl(-)) and water, whereas the lower tubule reabsorbs K(+) and Cl(-) but not water. The extent of KCl reabsorption by the lower tubule in vitro was monitored by ion-selective microelectrode measurement of Cl(-) and/or K(+) concentration in droplets of fluid secreted by Malpighian tubules isolated under oil. An earlier study proposed that K(+) reabsorption involves an omeprazole-sensitive apical K(+)/H(+) ATPase and Ba(2+)-sensitive basolateral K(+) channels. This paper examines the effects acetazolamide and of compounds that inhibit chloride channels, Cl(-)/HCO(3)(-) exchangers and Na(+)/K(+)/2Cl(-) or K(+)/Cl(-) co-transporters. The results suggest that Cl(-) reabsorption is inhibited by acetazolamide and by Cl(-) channel blockers, including diphenylamine-2-carboxylate(DPC) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), but not by compounds that block Na(+)/K(+)/Cl(-) and K(+)/Cl(-) co-transporters. Measurements of transepithelial potential and basolateral membrane potential during changes in bathing saline chloride concentration indicate the presence of DPC- and NPPB-sensitive chloride channels in the basolateral membrane. A working hypothesis of ion movements during KCl reabsorption proposes that Cl(-) moves from lumen to cell through a stilbene-insensitive Cl(-)/HCO(3)(-) exchanger and then exits the cell through basolateral Cl(-) channels.
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Affiliation(s)
- M J. O'Donnell
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Canada
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