THE EFFECT OF CORTISOL ON RECOVERY FROM EXHAUSTIVE EXERCISE IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) - POTENTIAL MECHANISMS OF ACTION

The effects of cortisol on metabolic recovery from exhaustive exercise in rainbow trout (Oncorhynchus mykiss) and potential mechanisms of ac tion were investigated. When the postexercise rise in cortisol is prev ented in fish by blocking either cortisol synthesis with metyrapone or cortisol release with dexamethasone, there is a faster recovery of bl ood and muscle metabolites and acid-base status in those fish than in control fish. To investigate whether preventing the rise in plasma cor tisol is responsible for these effects, two experiments were done. Cor tisol Infused into fish treated with metyrapone returned the rate of r ecovery to that of control fish. Treatment with 11-deoxycortisol or de oxycorticosterone, intermediates in the cortisol biosynthetic pathway the levels of which are possibly increased by metyrapone treatment, di d trot increase the rate of recovery; indeed, plasma cortisol rc,as el evated and recovery prolonged in fish treated with 11-deoxycortisol. T hese experiments indicate that preventing the postexercise rise in pla sma cortisol is associated with decreasing the rime required for metab olic and acid-base recovery. The mechanism of cortisol action is not a lteration of net acid excretion at the gills or mediated by some actio n at the RU486-sensitive cortisol receptor. It is suggested that corti sol may play an adaptive role in recovery from exhaustive exercise by providing lactate as a postexercise aerobic fuel.