title: Branchial ion exchange and acid-base regulation after strenuous exercise in rainbow trout (Salmo gairdneri).
abstract: Specimens of rainbow trout (Salmo gairdneri) were electrically stimulated to exhausting activity in a closed water recirculation system and the changes in dorsal aortic plasma pH, PCO2, PO2, O2 content, [Na+], [Cl-], [K+], [Lactate-] and Ht were measured during a 24 h recovery period. Net transfer of H+, Na+, Cl- and ammonia between fish and environment were determined by measurement of the concentration changes in the recirculating water. Strenuous exercise resulted in a severe lactacidosis which was corrected by transient net transfer of H+ ions to the environmental water within 4 h, about 6-8 h before the lactate was metabolically removed. The net transfer of H+ ions was achieved in part by branchial HCO3-/Cl- ion exchanges, but to a larger extent by branchial exchange of H+ and/or NH4+ against Na+. The excretion of ammonia, which was considerably enhanced during the first 4 h after exercise, was at least partially due to non-ionic diffusion across the gill epithelium. The observed elevation in ammonia excretion was probably the result of an exercise-induced increase in nitrogen metabolism rather than of production of ammonia for the purpose of acid-base regulation.
mesh_terms: D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D005880:Gills / Q000378:metabolism* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007474:Ion Exchange; D007773:Lactates; D005082:Physical Exertion; D012487:Salmonidae / Q000502:physiology*; D014337:Trout / Q000502:physiology*
chemical_list: D001639:Bicarbonates; D007773:Lactates; D000641:Ammonia