Pagnotta ,Antonella, Brooks, Linda & Milligan , Louise (1994) The potential regulatory roles of cortisol in recovery from exhaustive exercise in rainbow trout. Canadian Journal of Zoology 72 (12) 2136-2146.
Exercise to exhaustion,
as indicated by near depletion of muscle glycogen stores, resulted
in a 2- to 3-fold increase in the levels of plasma cortisol, but
there was no consistent effect of exercise on plasma insulin,
glucagon, T-3 or T-4 levels. Treatment of rainbow trout (Oncorhynchus
mykiss) with metyrapone (which inhibits cortisol synthesis) 1
h or dexamethasone (which inhibits cortisol release) 24 h prior
to exercise successfully blocked the exercise-induced rise in
plasma cortisol. Neither metyrapone nor dexamethasone treatment
had any effect on exercise performance, as muscle glycogen was
depleted and lactate accumulated to the same extent in control
and treated fish. Control fish showed the typical blood lactate
response to exhaustive exercise: (lactate) peaked at 10-15 mu-mol
cntdot mL-1 about 2 - 4 h post exercise and returned to pre-exercise
levels within 8 h. The response of blood lactate in cortisol-blocked
fish was significantly different: post-exercise levels were rarely
greater than 5 mu-mol cntdot mL-1 and had returned to resting
levels by 2 h. Analysis of tissue metabolite and acid -base status
indicated that cortisol-blocked fish recovered faster than did
controls. In treated fish, muscle glycogen and lactate levels
had returned to pre-exercise levels within 2 h. Blood pH and muscle
intracellular pH were also restored to pre-exercise values within
2 h. In contrast, restoration of tissue metabolite and acid -base
status in control fish required up to 8 h. The fact that both
metyrapone and dexamethasone treatment had the same effects on
recovery metabolism suggests that it is the absence of the rise
in plasma cortisol, rather than the drug treatment itself, which
is responsible for the enhancement of metabolic recovery.