The effects of prolonged epinephrine infusion on the physiology of the rainbow trout, Salmo gairdneri. III. Renal ionic fluxes.

Rainbow trout were infused continuously for 24 h with epinephrine in order to evaluate the effects of elevated circulating levels of epinephrine on selected renal variables. Pronounced effects of epinephrine included elevation of urine flow rate and concomitant increases in the excretion of all measured electrolytes (Na+, Cl-, K+, Ca2+, inorganic phosphate) with the exception of ammonium and bicarbonate ions. Significant reductions in the tubular reabsorption of Na+ and Cl- also contributed to enhanced excretion of these ions. Similarly, epinephrine affected the tubular handling of NH4+ and HCO3- with NH4+ secretion decreasing and HCO3- reabsorption increasing. We speculate that the stimulation of HCO3- reabsorption was a consequence of elevated tubular H+ secretion. Such a mechanism may be important to permit plasma HCO3- retention during periods of internal acidosis. The results are discussed with reference to the role of the fish kidney in regulating acid-base disturbances and the possible interactive effects of elevated epinephrine.