The role of catecholamines in erythrocyte pH regulation and oxygen transport in rainbow trout (Salmo gairdneri) during exercise.

Rainbow trout were subjected to burst swimming to exhaustion followed by 4 h aerobic swimming at 80% critical swimming velocity. Severe physiological disturbances, including a marked plasma acidosis caused by the burst swim, were corrected during the 4 h of subsequent aerobic exercise. Erythrocytic pH and arterial oxygen content increased, even though plasma pH was reduced. We suggest that the increase in erythrocytic pH was caused by the action of elevated adrenaline and noradrenaline levels in the blood acting on beta-adrenergic receptors on the trout red blood cell, causing the cell to swell and raising intracellular pH, offsetting any effect of a reduction of plasma pH on erythrocyte pH and haemoglobin-oxygen binding. Propranolol blocked the action of catecholamines on trout erythrocytes. We conclude that catecholamines play an important role in maintaining oxygen transport to aerobic muscles, following burst swimming and the associated acidotic conditions.