Ovarian stimulation by oestrogens: Effects in immature hypophysectomized rats

Abstract

The rapid fall in ovary weight that follows hypophysectomy in immature rats may be pre­vented if a tablet of stilboestrol is implanted when the pituitary gland is removed. Under this treatment the number of ovarian follicles greater than 200 μ in diameter is significantly increased though the size of the largest follicles in the ovary is unchanged. The follicles in the treated rats are predominantly solid. These facts suggest that oestrogen stimulates the proliferation of the membrana granulosa. The atrophy of the interstitial cells of the ovary is not prevented. When the stilboestrol is implanted 17 days after hypophysectomy only the few semi-mature follicles, which are not yet atrophied, are stimulated; the primordial follicles are unaffected. Injection of an amount of antigonadotrophic serum sufficient to neutralize the gonado­trophin secreted by the pituitary of an adult rat does not interfere with the ovarian stimula­tion produced by oestrogen. The daily absorption from the stilboestrol tablets is about 120 μ g. Similar effects are produced by the daily injection of 100 μ g. of oestrone. Stimulation is histologically demonstrable with daily injections of 12.5 μ g. of oestrone. These doses are not regarded as unphysiological for reasons which are discussed.