TY - JOUR
T1 - Intestinal ammonia transport in freshwater and seawater acclimated rainbow trout (Oncorhynchus mykiss)
T2 - Evidence for a Na+ coupled uptake mechanism
AU - Rubino, Julian G.
AU - Zimmer, Alex M.
AU - Wood, Chris M.
N1 - Funding Information:
Special thanks to Dr. Eric Clelland, Research Coordinator at BMSC, for providing his services thus allowing us the ability to perform this research, to Tiffany Chow, for her tremendous technical assistance in performing the gut sac experiments, to Tamzin Blewett, who began seawater acclimating the trout prior to our arrival at BMSC, and to Drs. Grant McClelland, Mike O'Donnell, and two anonymous reviewers for their helpful comments on the MS. This work was supported by a NSERC Discovery grant to CMW (Grant Number RGPIN743-12 ) who is also supported by the Canada Research Chair Program . AMZ is supported by a NSERC Canada Graduate Scholarship . All experiments performed in this study conformed to the animal care guidelines implemented by the Animal Care Committees at BMSC and McMaster University.
PY - 2015/5/1
Y1 - 2015/5/1
N2 - In vitro gut sac experiments were performed on freshwater and 60% seawater acclimated trout (Oncorhynchus mykiss) under treatments designed to discern possible mechanisms of intestinal ammonia transport. Seawater acclimation increased ammonia flux rate into the serosal saline (Jsamm) in the anterior intestine, however it did not alter Jsamm in the mid- or posterior intestine suggesting similar mechanisms of ammonia handling in freshwater and seawater fish. Both fluid transport rate (FTR) and Jsamm were inhibited in response to basolateral ouabain treatment, suggesting a linkage of ammonia uptake to active transport, possibly coupled to fluid transport processes via solvent drag. Furthermore, decreases in FTR and Jsamm caused by low Na+ treatment indicated a Na+ linked transport mechanism. Mucosal bumetanide (10-4M) had no impact on FTR, yet decreased Jsamm in the anterior and mid-intestine, suggesting NH4
+ substitution for K+ on an apical NKCC, and at least a partial uncoupling of ammonia transport from fluid transport. Additional treatments (amiloride, 5-(N-ethyl-N-isopropyl)amiloride (EIPA), phenamil, bafilomycin, 4',6-diamidino-2-phenylindole (DAPI), high sodium) intended to disrupt alternative routes of Na+ uptake yielded no change in FTR or Jsamm, suggesting the absence of direct competition between Na+ and ammonia for transport. Finally, [14C]methylamine permeability (PMA) measurements indicated the likely presence of an intestinal Rh-mediated ammonia transport system, as increasing NH4Cl (0, 1, 5mmoll-1) concentrations reduced PMA, suggesting competition for transport through Rh proteins. Overall, the data presented in this paper provide some of the first insights into mechanisms of teleost intestinal ammonia transport.
AB - In vitro gut sac experiments were performed on freshwater and 60% seawater acclimated trout (Oncorhynchus mykiss) under treatments designed to discern possible mechanisms of intestinal ammonia transport. Seawater acclimation increased ammonia flux rate into the serosal saline (Jsamm) in the anterior intestine, however it did not alter Jsamm in the mid- or posterior intestine suggesting similar mechanisms of ammonia handling in freshwater and seawater fish. Both fluid transport rate (FTR) and Jsamm were inhibited in response to basolateral ouabain treatment, suggesting a linkage of ammonia uptake to active transport, possibly coupled to fluid transport processes via solvent drag. Furthermore, decreases in FTR and Jsamm caused by low Na+ treatment indicated a Na+ linked transport mechanism. Mucosal bumetanide (10-4M) had no impact on FTR, yet decreased Jsamm in the anterior and mid-intestine, suggesting NH4
+ substitution for K+ on an apical NKCC, and at least a partial uncoupling of ammonia transport from fluid transport. Additional treatments (amiloride, 5-(N-ethyl-N-isopropyl)amiloride (EIPA), phenamil, bafilomycin, 4',6-diamidino-2-phenylindole (DAPI), high sodium) intended to disrupt alternative routes of Na+ uptake yielded no change in FTR or Jsamm, suggesting the absence of direct competition between Na+ and ammonia for transport. Finally, [14C]methylamine permeability (PMA) measurements indicated the likely presence of an intestinal Rh-mediated ammonia transport system, as increasing NH4Cl (0, 1, 5mmoll-1) concentrations reduced PMA, suggesting competition for transport through Rh proteins. Overall, the data presented in this paper provide some of the first insights into mechanisms of teleost intestinal ammonia transport.
KW - Ammonia
KW - Ammonia flux
KW - Bumetanide
KW - Fluid transport rate
KW - Intestine
KW - Na
KW - NKCC
KW - Ouabain
KW - Rh glycoproteins
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UR - http://www.scopus.com/inward/citedby.url?scp=84921503620&partnerID=8YFLogxK
U2 - 10.1016/j.cbpa.2014.12.037
DO - 10.1016/j.cbpa.2014.12.037
M3 - Article
AN - SCOPUS:84921503620
VL - 183
SP - 45
EP - 56
JO - Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology
JF - Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology
SN - 1095-6433
ER -