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Wennysia IC, Zhao L, Schomber T, Braun D, Golz S, Summer H, Benardeau A, Lai EY, Lichtenberger FB, Schubert R, Persson PB, Xu MZ, Patzak A. Role of soluble guanylyl cyclase in renal afferent and efferent arterioles. Am J Physiol Renal Physiol 2020; 320:F193-F202. [PMID: 33356952 DOI: 10.1152/ajprenal.00272.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Renal arteriolar tone depends considerably on the dilatory action of nitric oxide (NO) via activation of soluble guanylyl cyclase (sGC) and cGMP action. NO deficiency and hypoxia/reoxygenation are important pathophysiological factors in the development of acute kidney injury. It was hypothesized that the NO-sGC-cGMP system functions differently in renal afferent arterioles (AA) compared with efferent arterioles (EA) and that the sGC activator cinaciguat differentially dilates these arterioles. Experiments were performed in isolated, perfused mouse glomerular arterioles. Hypoxia (0.1% oxygen) was achieved by using a hypoxia chamber. Phosphodiesterase 5 (PDE5) and sGC subunits were considerably expressed on the mRNA level in AA. PDE5 inhibition with sildenafil, which blocks cGMP degradation, diminished the responses to ANG II bolus application in AA, but not significantly in EA. Vasodilation induced by sildenafil in ANG II-preconstricted vessels was stronger in EA than AA. Cinaciguat, an NO- and heme-independent sGC activator, dilated EA more strongly than AA after NG-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) treatment and preconstriction with ANG II. Cinaciguat-induced dilatation of l-NAME-pretreated and ANG II-preconstricted arterioles was similar to controls without l-NAME treatment. Cinaciguat also induced dilatation in iodinated contrast medium treated AA. Furthermore, it dilated EA, but not AA, after hypoxia/reoxygenation. The results reveal an important role of the NO-sGC-cGMP system for renal dilatation and that EA have a more potent sGC activated dilatory system. Furthermore, AA seem to be more sensitive to hypoxia/reoxygenation than EA under these experimental conditions.
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Affiliation(s)
- I C Wennysia
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - L Zhao
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.,Department of Physiology, School Basic Medical Sciences, Guangzhou Medical University, Guangzhou, China
| | - T Schomber
- Research & Development, Bayer AG, Wuppertal, Germany
| | - D Braun
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - S Golz
- Research & Development, Bayer AG, Wuppertal, Germany
| | - H Summer
- Research & Development, Bayer AG, Wuppertal, Germany
| | - A Benardeau
- Research & Development, Bayer AG, Wuppertal, Germany
| | - E Y Lai
- Department of Physiology, Zhejiang University School of Medicine, Hangzhou, China
| | - F-B Lichtenberger
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - R Schubert
- Physiology, Medical Faculty, Institute of Theoretical Medicine, University of Augsburg, Augsburg, Germany
| | - P B Persson
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - M Z Xu
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - A Patzak
- Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
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Aycan K, Ulcay T, Kamaşak B. The morphology of the afferent and efferent domain of the sheep glomerulus. Folia Morphol (Warsz) 2020; 80:881-887. [PMID: 33084008 DOI: 10.5603/fm.a2020.0124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 09/15/2020] [Accepted: 09/16/2020] [Indexed: 11/25/2022]
Abstract
BACKGROUND It is important to know the morphology of the glomerulus in order to explain kidney infiltration. The present study aims to research the morphology of afferent and efferent domains of sheep kidney glomeruli. MATERIALS AND METHODS In this study, 2000 glomeruli from 20 kidneys of Akkaraman sheep were examined using the polyester resin method. RESULTS It was found that the glomeruli of sheep kidney usually have an afferent arteriole as well as an efferent arteriole. Besides, it was also found that five glomeruli have two efferent arterioles. It is known that the afferent domain constitutes the largest part of the glomerulus. In two of the glomeruli that we examined, the afferent domain forms the ½ of the glomeruli wherein the other two glomeruli afferent domain forms the ¾. CONCLUSIONS It is known that there are many anastomoses between the afferent and efferent domain capillaries. However, it is not well-explained how anastomosis is created between the afferent and efferent domains. In our study, it was identified that those anastomoses are not inside the lobes but between the surrounding capillaries.
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Affiliation(s)
- K Aycan
- ahi evran university, faculty of medicine, department of anatomy, Bağbaşı, Şht. Sahir Kurutluoğlu Cd. No: 100, 40100 kırşehir, Turkey.
| | - T Ulcay
- ahi evran university, faculty of medicine, department of anatomy, Bağbaşı, Şht. Sahir Kurutluoğlu Cd. No: 100, 40100 kırşehir, Turkey
| | - B Kamaşak
- ahi evran university, faculty of medicine, department of anatomy, Bağbaşı, Şht. Sahir Kurutluoğlu Cd. No: 100, 40100 kırşehir, Turkey
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Razga Z. Functional Relevancies of Trans-Differentiation in the Juxtaglomerular Apparatus of Rat Kidney. Int J Nephrol Renovasc Dis 2020; 13:147-156. [PMID: 32606889 PMCID: PMC7297338 DOI: 10.2147/ijnrd.s246476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 05/09/2020] [Indexed: 12/17/2022] Open
Abstract
Glomerular filtration rate is controlled by the contractile effect of angiotensin II on afferent and efferent arterioles. The renin positivity of the afferent arterioles depends on tubuloglomerular feedback via the macula densa (MD) and short loop feedback via the afferent arteriolar endothelia. The renin-producing cells are trans-differentiated from smooth muscle cells (SMCs) of mainly the afferent arterioles, the MD cells are trans-differentiated from the neighboring tubular cells, and the high-permeability endothelial cells are trans-differentiated from normal permeability endothelial cells facing the renin-negative part of the afferent arterioles. All of the trans-differentiations depend on the activity of the renin-angiotensin system (RAS). The distribution of AT1 receptors for angiotensin II expresses the contractile effects of angiotensin II on renin-negative SMCs and the negative effect on trans-differentiation of renin-positive SMCs and MD cells. The purpose of this review is to summarize the stereological data of molecules like angiotensin II AT1 receptors, L-type calcium channels, and renin receptors in the juxtaglomerular apparatus of normal and STZ-induced diabetic rat kidneys, thus showing their functional relevancies on trans-differentiation among the juxtaglomerular apparatus’ elements.
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Affiliation(s)
- Zsolt Razga
- Department of Pathology, University of Szeged, Szeged, Hungary
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Shao W, Rosales CB, Gonzalez C, Prieto MC, Navar LG. Effects of serelaxin on renal microcirculation in rats under control and high-angiotensin environments. Am J Physiol Renal Physiol 2018; 314:F70-F80. [PMID: 28978531 DOI: 10.1152/ajprenal.00201.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Serelaxin is a novel recombinant human relaxin-2 that has been investigated for the treatment of acute heart failure. However, its effects on renal function, especially on the renal microcirculation, remain incompletely characterized. Our immunoexpression studies localized RXFP1 receptors on vascular smooth muscle cells and endothelial cells of afferent arterioles and on principal cells of collecting ducts. Clearance experiments were performed in male and female normotensive rats and Ang II-infused male rats. Serelaxin increased mean arterial pressure slightly and significantly increased renal blood flow, urine flow, and sodium excretion rate. Group analysis of all serelaxin infusion experiments showed significant increases in GFR. During infusion with subthreshold levels of Ang II, serelaxin did not alter mean arterial pressure, renal blood flow, GFR, urine flow, or sodium excretion rate. Heart rates were elevated during serelaxin infusion alone (37 ± 5%) and in Ang II-infused rats (14 ± 2%). In studies using the in vitro isolated juxtamedullary nephron preparation, superfusion with serelaxin alone (40 ng/ml) significantly dilated afferent arterioles (10.8 ± 1.2 vs. 13.5 ± 1.1 µm) and efferent arterioles (9.9 ± 0.9 vs. 11.9 ± 1.0 µm). During Ang II superfusion, serelaxin did not alter afferent or efferent arteriolar diameters. During NO synthase inhibition (l-NNA), afferent arterioles also did not show any vasodilation during serelaxin infusion. In conclusion, serelaxin increased overall renal blood flow, urine flow, GFR, and sodium excretion and dilated the afferent and efferent arterioles in control conditions, but these effects were attenuated or prevented in the presence of exogenous Ang II and NO synthase inhibitors.
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Affiliation(s)
- Weijian Shao
- Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine , New Orleans, Louisiana
| | - Carla B Rosales
- Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine , New Orleans, Louisiana
| | - Camila Gonzalez
- Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine , New Orleans, Louisiana
| | - Minolfa C Prieto
- Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine , New Orleans, Louisiana
| | - L Gabriel Navar
- Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine , New Orleans, Louisiana
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Zhao L, Gao Y, Cao X, Gao D, Zhou S, Zhang S, Cai X, Han F, Wilcox CS, Li L, Lai EY. High-salt diet induces outward remodelling of efferent arterioles in mice with reduced renal mass. Acta Physiol (Oxf) 2017; 219:652-659. [PMID: 27454938 DOI: 10.1111/apha.12759] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 06/04/2016] [Accepted: 07/19/2016] [Indexed: 01/01/2023]
Abstract
AIM The glomerular filtration rate (GFR) falls progressively in chronic kidney disease (CKD) which is caused by a reduction in the number of functional nephrons. The dysfunctional nephron exhibits a lower glomerular capillary pressure that is induced by an unbalance between afferent and efferent arteriole. Therefore, we tested the hypothesis that oxidative stress induced by CKD differentially impairs the structure or function of efferent vs. afferent arterioles. METHODS C57BL/6 mice received sham operations (sham) or 5/6 nephrectomy (RRM) and three months of normal- or high-salt diet or tempol. GFR was assessed from the plasma inulin clearance, arteriolar remodelling from media/lumen area ratio, myogenic responses from changes in luminal diameter with increases in perfusion pressure and passive wall compliance from the wall stress/strain relationships. RESULTS Mice with RRM fed a high salt (vs. sham) had a lower GFR (553 ± 25 vs. 758 ± 36 μL min-1 g-1 kidney, P < 0.01) and a larger efferent arteriolar diameter (9.6 ± 0.8 vs. 7.4 ± 0.7 μm, P < 0.05) resulting in a lower media/lumen area ratio (1.4 ± 0.1 vs. 2.4 ± 0.2, P < 0.01). These alterations were corrected by tempol. The myogenic responses of efferent arterioles were about one-half that of afferent arterioles and were unaffected by RRM or salt. Passive wall compliance was reduced by high salt in both afferent and efferent arterioles. CONCLUSION A reduction in renal mass with a high-salt diet induces oxidative stress that leads to an outward eutrophic remodelling in efferent arterioles and reduced wall compliance in both afferent and efferent arterioles. This may contribute to the lower GFR in this model of CKD.
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Affiliation(s)
- L. Zhao
- Department of Physiology; Zhejiang University School of Medicine; Hangzhou China
| | - Y. Gao
- Department of Physiology; Zhejiang University School of Medicine; Hangzhou China
| | - X. Cao
- Department of Physiology; Zhejiang University School of Medicine; Hangzhou China
| | - D. Gao
- Department of Cardiology; The First Affiliated Hospital; Zhejiang University School of Medicine; Hangzhou China
| | - S. Zhou
- Department of Physiology; Zhejiang University School of Medicine; Hangzhou China
| | - S. Zhang
- Department of Physiology; Zhejiang University School of Medicine; Hangzhou China
| | - X. Cai
- Department of Physiology; Zhejiang University School of Medicine; Hangzhou China
- Department of Basic Medicine; Honghe Health Vocational College; Mengzi China
| | - F. Han
- Institute of Pharmacology and Toxicology; College of Pharmaceutical Sciences; Zhejiang University; Hangzhou China
| | - C. S. Wilcox
- Division of Nephrology and Hypertension; Hypertension, Kidney and Vascular Health Center; Georgetown University; Washington DC USA
| | - L. Li
- Division of Nephrology and Hypertension; Hypertension, Kidney and Vascular Health Center; Georgetown University; Washington DC USA
| | - E. Y. Lai
- Department of Physiology; Zhejiang University School of Medicine; Hangzhou China
- Division of Nephrology and Hypertension; Hypertension, Kidney and Vascular Health Center; Georgetown University; Washington DC USA
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Abstract
Endothelin (ET) is one of the most potent renal vasoconstrictors. Endothelin plays an essential role in the regulation of renal blood flow, glomerular filtration, sodium and water transport, and acid-base balance. ET-1, ET-2, and ET-3 are the three distinct endothelin isoforms comprising the endothelin family. ET-1 is the major physiologically relevant peptide and exerts its biological activity through two G-protein-coupled receptors: ET(A) and ET(B). Both ET(A) and ET(B) are expressed by the renal vasculature. Although ET(A) are expressed mainly by vascular smooth muscle cells, ET(B) are expressed by both renal endothelial and vascular smooth muscle cells. Activation of the endothelin system, or overexpression of downstream endothelin signaling pathways, has been implicated in several pathophysiological conditions including hypertension, acute kidney injury, diabetic nephropathy, and immune nephritis. In this review, we focus on the effects of endothelin on the renal microvasculature, and update recent findings on endothelin in the regulation of renal hemodynamics.
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Affiliation(s)
- Zhengrong Guan
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
| | - Justin P VanBeusecum
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
| | - Edward W Inscho
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL.
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Thuesen AD, Andersen H, Cardel M, Toft A, Walter S, Marcussen N, Jensen BL, Bie P, Hansen PBL. Differential effect of T-type voltage-gated Ca2+ channel disruption on renal plasma flow and glomerular filtration rate in vivo. Am J Physiol Renal Physiol 2014; 307:F445-52. [PMID: 24966091 DOI: 10.1152/ajprenal.00016.2014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Voltage-gated Ca(2+) (Cav) channels play an essential role in the regulation of renal blood flow and glomerular filtration rate (GFR). Because T-type Cav channels are differentially expressed in pre- and postglomerular vessels, it was hypothesized that they impact renal blood flow and GFR differentially. The question was addressed with the use of two T-type Cav knockout (Cav3.1(-/-) and Cav3.2(-/-)) mouse strains. Continuous recordings of blood pressure and heart rate, para-aminohippurate clearance (renal plasma flow), and inulin clearance (GFR) were performed in conscious, chronically catheterized, wild-type (WT) and Cav3.1(-/-) and Cav3.2(-/-) mice. The contractility of afferent and efferent arterioles was determined in isolated perfused blood vessels. Efferent arterioles from Cav3.2(-/-) mice constricted significantly more in response to a depolarization compared with WT mice. GFR was increased in Cav3.2(-/-) mice with no significant changes in renal plasma flow, heart rate, and blood pressure. Cav3.1(-/-) mice had a higher renal plasma flow compared with WT mice, whereas GFR was indistinguishable from WT mice. No difference in the concentration response to K(+) was observed in isolated afferent and efferent arterioles from Cav3.1(-/-) mice compared with WT mice. Heart rate was significantly lower in Cav3.1(-/-) mice compared with WT mice with no difference in blood pressure. T-type antagonists significantly inhibited the constriction of human intrarenal arteries in response to a small depolarization. In conclusion, Cav3.2 channels support dilatation of efferent arterioles and affect GFR, whereas Cav3.1 channels in vivo contribute to renal vascular resistance. It is suggested that endothelial and nerve localization of Cav3.2 and Cav3.1, respectively, may account for the observed effects.
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Affiliation(s)
- Anne D Thuesen
- Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Henrik Andersen
- Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Majken Cardel
- Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Anja Toft
- Department of Urology, Odense University Hospital, Odense, Denmark; and
| | - Steen Walter
- Department of Urology, Odense University Hospital, Odense, Denmark; and
| | - Niels Marcussen
- Clinical Pathology, Odense University Hospital, Odense, Denmark
| | - Boye L Jensen
- Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Peter Bie
- Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Pernille B L Hansen
- Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark;
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Abstract
1. The early stage of type 1 diabetes mellitus (DM) is characterized by renal hyperfiltration, which promotes the eventual development of diabetic nephropathy. The hyperfiltration state is associated with afferent arteriolar dilation and diminished responsiveness of this vascular segment to a variety of vasoconstrictor stimuli, whereas efferent arteriolar diameter and vasoconstrictor responsiveness are typically unaltered. 2. The contractile status of preglomerular vascular smooth muscle appears to be tightly coupled to membrane potential (E(m)) and its influence on Ca(2+) influx through voltage-gated channels. Efferent arteriolar tone is largely independent of electromechanical events. Hence, defective electromechanical mechanisms in vascular smooth muscle should engender selective changes in preglomerular microvascular function, such as those evident during the early stage of DM. 3. Afferent arteriolar contractile responses to K(+)-induced depolarization and BAYK8644 are diminished 2 weeks after onset of DM in the rat. Similarly, depolarization-induced Ca(2+) influx and the resulting increase in intracellular [Ca(2+)] are abated in the preglomerular microvasculature of diabetic rats. The intracellular [Ca(2+)] response to depolarization is rapidly restored by normalization of extracellular glucose levels. These observations suggest that hyperglycaemia in DM impairs regulation of afferent arteriolar voltage-gated Ca(2+) channels. 4. Dysregulation of E(m) may also contribute to afferent arteriolar dilation in DM. Vasodilator responses to pharmacological opening of ATP-sensitive K(+) channels are exaggerated in afferent arterioles from diabetic rats. Moreover, blockade of these channels normalizes afferent arteriolar diameter in kidneys from diabetic rats. These observations suggest that increased functional availability and basal activation of ATP-sensitive K(+) channels promote afferent arteriolar dilation in DM. 5. We propose that dysregulation of E(m) (involving ATP- sensitive K(+) channels) and a diminished Ca(2+) influx response to depolarization (involving voltage-gated Ca(2+) channels) may act synergistically to promote preglomerular vasodilation during the early stage of DM.
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Affiliation(s)
- Pamela K Carmines
- Department of Physiology and Biophysics, University of Nebraska College of Medicine, Omaha, Nebraska 68198-4575, USA.
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Fallet RW, Bast JP, Fujiwara K, Ishii N, Sansom SC, Carmines PK. Influence of Ca(2+)-activated K(+) channels on rat renal arteriolar responses to depolarizing agonists. Am J Physiol Renal Physiol 2001; 280:F583-91. [PMID: 11249849 PMCID: PMC2570964 DOI: 10.1152/ajprenal.2001.280.4.f583] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Experiments were performed to evaluate the hypothesis that opening of Ca(2+)-activated K(+) channels (BK(Ca) channels) promotes juxtamedullary arteriolar dilation and curtails constrictor responses to depolarizing agonists. Under baseline conditions, afferent and efferent arteriolar lumen diameters averaged 23.4 +/- 0.9 (n = 36) and 22.8 +/- 1.1 (n = 13) microm, respectively. The synthetic BK(Ca) channel opener NS-1619 evoked concentration-dependent afferent arteriolar dilation. BK(Ca) channel blockade (1 mM tetraethylammonium; TEA) decreased afferent diameter by 15 +/- 3% and prevented the dilator response to 30 microM NS-1619. ANG II (10 nM) decreased afferent arteriolar diameter by 44 +/- 4%, a response that was reduced by 30% during NS-1619 treatment; however, TEA failed to alter afferent constrictor responses to either ANG II or arginine vasopressin. Neither NS-1619 nor TEA altered agonist-induced constriction of the efferent arteriole. Thus, although the BK(Ca) channel agonist was able to curtail afferent (but not efferent) arteriolar constrictor responses to ANG II, BK(Ca) channel blockade did not allow exaggerated agonist-induced arteriolar constriction. These observations suggest that the BK(Ca) channels evident in afferent arteriolar smooth muscle do not provide a prominent physiological brake on agonist-induced constriction under our experimental conditions.
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Affiliation(s)
- R W Fallet
- Department of Physiology and Biophysics, University of Nebraska College of Medicine, Omaha, Nebraska 68198-4575, USA
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10
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Abstract
Experiments were performed to test the hypothesis that tyrosine kinase activity contributes to renal arteriolar contractile responses to angiotensin (Ang) II. Rats were subjected to short-term enalaprilat treatment to decrease endogenous Ang II formation before tissue was harvested for experiments with the in vitro blood-perfused juxtamedullary nephron technique. Acute surgical papillectomy was used to avoid the indirect afferent arteriolar effect of Ang II that arises through increased tubuloglomerular feedback sensitivity. Arteriolar lumen diameter responses to 1 and 10 nmol/L Ang II were monitored by videomicroscopic methods before and during treatment with various tyrphostin compounds: 100 micromol/L AG18 (broad-spectrum tyrosine kinase inhibitor), 100 nmol/L AG1478 (selective epidermal growth factor receptor tyrosine kinase inhibitor), or 100 micromol/L AG9 (inactive analog). Baseline afferent arteriolar lumen diameter averaged 23.5+/-1.2 micrometer and was not influenced by any tyrphostin. Ang II (10 nmol/L) decreased afferent diameter by 11.1+/-1.0 micrometer under untreated conditions, a response that was not altered by AG9 but significantly blunted by AG18 (34+/-9% inhibition) or AG1478 (52+/-8% inhibition). AG18 did not suppress afferent arteriolar contractile responses to membrane depolarization (20 to 55 mmol/L K(+ )bath). Efferent arteriolar baseline diameter averaged 24.1+/-0.8 micrometer and was unaltered by AG18 or AG1478; however, efferent diameter responses to 10 nmol/L Ang II were diminished 52+/-10% by AG18 and 51+/-13% by AG1478. These observations indicate that Ang II signaling in renal afferent and efferent arteriolar vascular smooth muscle is either mediated or modulated by tyrosine kinase activity, including that of the epidermal growth factor receptor tyrosine kinase.
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Affiliation(s)
- P K Carmines
- Department of Physiology and Biophysics, University of Nebraska Medical Center, Omaha, NE, USA.
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