Biological effects of single and repeated swimming stress in male rats: beneficial effects of glucocorticoids.

We have examined the biological effects of single (45 min at 22 degrees C) and repeated swimming stress (45 min at 22 degrees C for 7 d) using male Sprague-Dawley rats. Repeated swimming for a week resulted in a significant inhibition in total body weight (25%) as compared to control unstressed animals. There was significant increase in adrenal and kidney relative weight and decreases in relative thymus weight in repeated swimming-stressed animals as compared to control animals. Repeated swimming stress resulted in almost threefold increase in plasma corticosterone levels with concomitant dramatic decrease in total glucocorticoid receptor (GR) levels in liver, thymus, and heart as compared to control unstressed animals. Interestingly, single swimming stress resulted in a significant elevation in lipid peroxidation levels in the liver and heart. In contrast, there was no change in the lipid per oxidation levels in the liver and heart between chronic stressed and control unstressed animals. Finally, both single and repeated swimming-stress animals had almost 50% reduction in plasma triglyceride levels as compared to control unstressed animals. It is concluded that elevated plasma corticosterone levels by downregulating GR during repeated swimming stress exerts beneficial effects in rats by retarding the total body weight gain and lowering plasma triglyceride levels without affecting free-radicals-induced oxidative stress.