Experiments were carried out to investigate the relationship between ion exchange and energy metabolism in rainbow trout erythrocytes in vitro. Under resting conditions, the sodium/potassium pump accounts for 20 % of the cellular energy budget. In the presence of the β-adrenergic agonist isoproterenol, however, this increases to 43 %. Inhibition of the sodium/potassium pump with ouabain results in greater increases in erythrocyte water content and sodium and chloride concentrations and a greater decrease in erythrocyte potassium concentration following stimulation by isoproterenol. Moreover, the decrease in erythrocyte NTP levels observed following adrenergic stimulation does not occur when the sodium/potassium pump is inhibited with ouabain. Inhibition of the sodium/potassium pump also abolishes the increase in oxygen consumption by the cells which normally takes place following adrenergic stimulation. Finally, depletion of erythrocyte NTP levels by the sodium ionophore monensin or by previous incubation with nitrogen does not result in a significant increase in oxygen consumption. Thus, catecholamines appear to be crucial for the metabolic-membrane coupling that occurs following adrenergic stimulation in rainbow trout erythrocytes.

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