Effects of castration on adipose tissue growth and regrowth in the male rat

Adipose tissue has been found to regrow in the male rat following surgical removal (lipectomy) of inguinal subcutaneous depots, but the degree of regrowth has varied widely across experiments. It is possible that at least part of the disparity of previous findings occurred because of differences among the experiments in the testicular integrity of experimental animals. To address this possibility, the present study examined effects of castration on adipose tissue regrowth in rats treated either as weanlings or as young adults. Male Sprague-Dawley rats, at either 4 or 15 weeks of age, were subjected to one of four surgical procedures: bilateral lipectomy of the inguinal subcutaneous depots; castration; lipectomy and weight gain, but castrated rats achieved a higher ratio of adipose weight to body weight than noncastrated rats. In rats lipectomized but not castrated at 15 weeks of age, partial regeneration and a small increase in growth of noninguinal subcutaneous adipose tissue combined to produce substantial restoration of adipose mass. The same surgery in 4-week-old rats did not result in significant restoration because growth of noninguinal subcutaneous adipose tissue was reduced. In rats that were both castrated and lipectomized, regrowth of adipose tissue was substantial regardless of age at time of surgery. Thus, castration is seen to impede body weight gain while sparing ordinary growth of adipose tissue and facilitating regrowth of adipose tissue following lipectomy. Since adipose tissue regrowth varied with age only in noncastrated rats, it appears to be facilitated as well by testicular maturation.