No abstract

Ovulation was induced in mature female rats by appropriately timed injections of pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (HCG). Various combinations of the gonadotrophins were used. Maximal ovulatory response was consistently obtained with 50 I.U. PMSG and any combination of HCG between 50 I.U. and 5000 I.U. On the basis of the results obtained it is recommended that 50 I.U. PMSG and 50 I.U. HCG be injected to obtain a maximal ovulatory response in mature rats. High doses of PMSG (but not HCG) suppress ovulation markedly.

The chronic administration of norethynodrel–mestranol to both mature and immature rats leads to an increase in hypophysial STH content. Our results suggest that this increase in STH content results from a decrease in the secretion of STH-RF or an increase in the secretion of STH-IF. The decrease in plasma STH-like activity would reflect this inhibition in STH-RF secretion. This is re-fleeted finally in retarded osteogenesis and growth.