Carbonic anhydrase (acetazolamide-sensitive esterase) activity in the red blood cells of thermally-acclimated rainbow trout, salmo gairdneri

Abstract

1. 1. “Membrane” and “cytosol” carbonic anhydrase activities were assayed by the p-nitrophenyl acetate method in rainbow trout acclimated to 2, 10 and 18°C. 2. 2. “Membrane” and “cytosol” protein concentrations varied inversely with temperature. 3. 3. Increases in acclimation temperature were, however, accompanied by increases in specific activity, and activity per unit volume of erythrocytes. 4. 4. As hematocrit increased significantly at higher acclimation temperatures estimated whole blood carbonic anhydrase was sharply elevated in warm—as compared to cold—acclimated specimens. 5. 5. Variations in activity with temperature were correlated with concomitant changes in erythrocytic chloride concentrations, and were also consistent with the role proposed for the red cell carbonic anhydrase system in amplification of branchial chloride uptake under elevated temperature conditions.