Effects of adrenaline on ionic equilibria in red blood cells of rainbow trout (Salmo gairdneri).

Effects of adrenaline on the equilibrium distributions of Na(+) , K(+) , H(+) , Cl(-) , and H2O across the cell membrane of rainbow trout (Salmo gairdneri) erythrocytes were determinedin vitro, as a function of P CO2 (1.76-7.77 torr). CO2-carrying capacity of the blood was also examined. Plasma catecholamine concentrations inunanaesthetized, unrestrained trout were 3.1 nM adrenaline and 1.2 nM noradrenaline. Elevation of the plasma adrenaline concentrationin vitro to 4.6 × 10(3) nM resulted in net gains of Na(+) , Cl(-) and H2O by red cells, a net loss of H(+) from red cells, and a pronounced red cell swelling. Adrenaline also reduced the CO2-carrying capacity of trout bloodin vitro. The magnitudes of these effects increased with PCO2 and, thus, were sensitive to blood HCO3 (-) concentrations. The distribution of K(+) between red cells and plasma was unaffected by adrenaline. Adrenergic-mediated ion movements and red cell swelling were sensitive to both propranolol and SITS. These results are consistent with the symport NaCl uptake model for adrenergic-mediated swelling of Baroinet al. (1984). The adrenergic response of fish erythrocytes may function to ameliorate the effects of blood acidoses on O2-carrying capacity by maintaining red cell pH in the face of a decrease in plasma pH.