Effects of Prepubertal Forced Exercise upon Postpubertal Organ and Body Weights of Female Rats

Abstract

One-hundred-fifty female rats were used in this study of the immediate and residual effects of prepubertal exercise upon organ and body weights. Animals were randomly assigned to 3 initial treatment groups: sedentary (S), voluntary (V), and voluntary plus forced exercise (V+F). Forced exercise consisted of 35 daily 30-min. swims with a tail weight of 2% of body weight. Two treatment periods were given, one just before puberty and another after 165 days of intervening voluntary activity. Sacrifices occurred posttreatment I, pretreatment II, and posttreatment II. Both (V) and (V+F) animals had lower body and absolute spleen weights but higher relative adrenal, heart, and liver weights than the controls. The absolute spleen and relative adrenal differences remained pretreatment II. Posttreatment II, lower body and absolute spleen weights were noted in (V) than in (S) groups. Although several significant interactions between treatments I and II were observed, only the lower body weight of active animals observed after treatment I was compounded by treatment II. Comparing the results of this study with a study of male rats, prepubertal body and organ weights showed a similar pattern, whereas, postpubertal measures were generally different. Voluntary activity is suggested to underlie the sexspecific response.