Journal of Applied Physiology, Vol 44, Issue 1 104-108, Copyright © 1978 by American Physiological Society
Adrenocortical function in response to myocardial necrosis in exercise-trained rats
J. A. Severson, R. D. Fell and D. R. Griffith
Plasma corticosterone concentrations and in vitro adrenal secretion of
corticosterone was determined in exercise-trained rats. Virgin, male rats,
100 days of age, were trained for an 11-wk period by treadmill running.
Following the training program, rats were subjected to two subcutaneous
injections of l-isoproterenol 24 h apart and killed 24 h after the second
injection. All exercise-trained rats survived isoproterenol treatment,
while 44% of the control rats died. Plasma corticosterone concentrations
were elevated only in exercise-trained rats treated with isoproterenol.
Control rats treated with isoproterenol had plasma corticosterone
concentrations similar to that in control and exercise-treated rats given
placebo injections. Exercise training reduced adrenocortical responsiveness
to ACTH in vitro, but isoproterenol treatment increased in vitro
responsiveness to ACTH in exercise-trained and control rats. Total
unstimulated corticosterone secretion rates in vitro were similar. The
reason for better rat survival in exercise-trained rats is unknown;
however, improved energy metabolism, depressed aldosterone secretion, or
both are suggested as reasons for the better survival of exercise-trained
rats.
