Hormonal contraceptive like effect of estrogen in milk protein-fed male rats

Adult male rats received daily injections (sc) of estradiol-17 beta (50 microg/100 g body wt per day) for 7 days. When they were sacrificed 14 days after the last injection, serum levels of gonadotropins and testosterone and weights of accessory sex organs were decreased significantly, testicular 17-hydroxysteroid dehydroganase activity was suppressed and spermatogenesis was inhibited in 5.0% casein-fed estrogen-treated rats. Feeding of 20.0% casein diet to estrogen-treated rats resulted in increased serum concentration of gonadotropins and testosterone. LH and testosterone appeared to be normal in 20.0% casein-fed estrogen-treated rats while serum FSH levels remained subnormal. The estrogen-treated rats fed on 20.0% casein diet showed decreased spermatogenesis in comparison with control rats fed on 20.0% casein diet. Together, these results indicate that high casein diet stimulates synthesis of testicular testosterone and increases serum LH levels more than FSH in estrogen-treated rats. It is concluded that estrogen in the presence of high milk protein diet may be considered to be a suitable steroid hormone in the development of a male contraceptive.