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Hoogenboom JL, Anderson WG. Investigating nitrogen movement in North Pacific spiny dogfish (Squalus acanthias suckleyi), with focus on UT, Rhp2, and Rhbg mRNA abundance. J Comp Physiol B 2023:10.1007/s00360-023-01487-4. [PMID: 37162540 DOI: 10.1007/s00360-023-01487-4] [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] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 03/15/2023] [Accepted: 04/14/2023] [Indexed: 05/11/2023]
Abstract
For ureosmotic marine elasmobranchs, the acquisition and retention of nitrogen is critical for the synthesis of urea. To better understand whole-body nitrogen homeostasis, we investigated mechanisms of nitrogen trafficking in North Pacific spiny dogfish (Squalus acanthias suckleyi). We hypothesized that the presence of nitrogen within the spiral valve lumen would affect both the transport of nitrogen and the mRNA abundance of a urea transporter (UT) and two ammonia transport proteins (Rhp2, Rhbg) within the intestinal epithelium. The in vitro preincubation of intestinal tissues in NH4Cl, intended to simulate dietary nitrogen availability, showed that increased ammonia concentrations did not significantly stimulate the net uptake of total urea or total methylamine. We also examined the mRNA abundance of UT, Rhp2, and Rhbg in the gills, kidney, liver, and spiral valve of fasted, fed, excess urea fed, and antibiotic-treated dogfish. After fasting, hepatic UT mRNA abundance was significantly lower, and Rhp2 mRNA in the gills was significantly higher than the other treatments. Feeding significantly increased Rhp2 mRNA levels in the kidney and mid spiral valve region. Both excess urea and antibiotics significantly reduced Rhbg mRNA levels along all three spiral valve regions. The antibiotic treatment also significantly diminished UT mRNA abundance levels in the anterior and mid spiral valve, and Rhbg mRNA levels in the kidney. In our study, no single treatment had significantly greater influence on the overall transcript abundance of the three transport proteins compared to another treatment, demonstrating the dynamic nature of nitrogen balance in these ancient fish.
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Affiliation(s)
- J Lisa Hoogenboom
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada.
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC, V0R 1B0, Canada.
| | - W Gary Anderson
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC, V0R 1B0, Canada
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White LJ, Rose M, Lawson M, Joyce D, Smith AM, Thomas GH, Dasmahapatra KK, Pownall ME. Two closely related ureotelic fish species of the genus Alcolapia express different levels of ammonium transporters in gills. Biol Open 2022; 11:277826. [PMID: 36250323 DOI: 10.1242/bio.059575] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [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: 08/09/2022] [Accepted: 10/10/2022] [Indexed: 11/20/2022] Open
Abstract
Most fish excrete their nitrogenous waste across the gills as ammonia through the activity of the Rhesus glycoprotein ammonium transporters. In contrast, fish of the subgenus Alcolapia (Oreochromis) are the only vertebrates that survive the extreme conditions of the soda lakes of Natron and Magadi in East Africa and have evolved adaptations to the highly alkaline waters including the ability to excrete their nitrogenous waste as urea. Nevertheless, Alcolapia retain the Rhesus glycoprotein genes in their genomes and using two heterologous expression systems, we demonstrate that Alcolapia Rhbg is capable of moving ammonia. Comparing ammonia and urea excretion from two closely related Alcolapia species from the same aquarium, we found that while Alcolapia grahami remains fully ureotelic after many generations in lab conditions, Alcolapia alcalica excretes some of its nitrogenous waste as ammonia. Using in situ hybridisation, we demonstrate robust, localised gene expression of Rhbg, rhcg1 and rhcg2 in the gill tissue in both A. alcalica embryos and adults, similar to that in other ammoniotelic fish. In contrast, the expression of these genes in A. grahami gills is much lower than in A. alcalica, suggesting the rapid evolution of a molecular mechanism underlying the complete ureotelism of A. grahami.
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Affiliation(s)
- Lewis J White
- Department of Biology, University of York, York, YO10 5DD, UK
| | - Matthew Rose
- Department of Biology, University of York, York, YO10 5DD, UK
| | - Michael Lawson
- Department of Biology, University of York, York, YO10 5DD, UK
| | - Domino Joyce
- Department of Biological and Marine Sciences, Faculty of Science and Engineering, University of Hull, Hull, HU6 7RX, UK
| | - Alan M Smith
- Department of Biological and Marine Sciences, Faculty of Science and Engineering, University of Hull, Hull, HU6 7RX, UK
| | - Gavin H Thomas
- Department of Biology, University of York, York, YO10 5DD, UK
| | | | - Mary E Pownall
- Department of Biology, University of York, York, YO10 5DD, UK
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Caner T, Abdulnour-Nakhoul S, Brown K, Islam MT, Hamm LL, Nakhoul NL. Mechanisms of ammonia and ammonium transport by rhesus-associated glycoproteins. Am J Physiol Cell Physiol 2015; 309:C747-58. [PMID: 26354748 DOI: 10.1152/ajpcell.00085.2015] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [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: 03/23/2015] [Accepted: 09/02/2015] [Indexed: 01/24/2023]
Abstract
In this study we characterized ammonia and ammonium (NH3/NH4(+)) transport by the rhesus-associated (Rh) glycoproteins RhAG, Rhbg, and Rhcg expressed in Xenopus oocytes. We used ion-selective microelectrodes and two-electrode voltage clamp to measure changes in intracellular pH, surface pH, and whole cell currents induced by NH3/NH4(+) and methyl amine/ammonium (MA/MA(+)). These measurements allowed us to define signal-specific signatures to distinguish NH3 from NH4(+) transport and to determine how transport of NH3 and NH4(+) differs among RhAG, Rhbg, and Rhcg. Our data indicate that expression of Rh glycoproteins in oocytes generally enhanced NH3/NH4(+) transport and that cellular changes induced by transport of MA/MA(+) by Rh proteins were different from those induced by transport of NH3/NH4(+). Our results support the following conclusions: 1) RhAG and Rhbg transport both the ionic NH4(+) and neutral NH3 species; 2) transport of NH4(+) is electrogenic; 3) like Rhbg, RhAG transport of NH4(+) masks NH3 transport; and 4) Rhcg is likely to be a predominantly NH3 transporter, with no evidence of enhanced NH4(+) transport by this transporter. The dual role of Rh proteins as NH3 and NH4(+) transporters is a unique property and may be critical in understanding how transepithelial secretion of NH3/NH4(+) occurs in the renal collecting duct.
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Affiliation(s)
- Tolga Caner
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - Solange Abdulnour-Nakhoul
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - Karen Brown
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - M Toriqul Islam
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - L Lee Hamm
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - Nazih L Nakhoul
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
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