Effects of 17β-hydroxy-7α-methylandrost-5-en-3-one on early pregnancy in the rat

Abstract

Abstract. A single sc injection of 1 mg 17β-hydroxy-7α-methylandrost-5-en-3-one (RMI-12,936) given a few hours after mating interrupted pregnancy in all the treated rats. Circulating progesterone (Δ4P) levels were higher in RMI-12,936 treated females than in controls on the corresponding days during the course of termination of pregnancy. Higher levels of Δ4P were recorded on day-4 (P < 0.01) and day-6 (P< 0.05) of pregnancy. In addition to the changes in serum Δ4P, an acceleration of egg transport was encountered. The eggs were prematurely expelled from the uterus within 48 h of the treatment. Although the oestrous cycle of the RMI-12,936 treated females was disturbed, they were found sexually receptive. Successful matings resulting in normal gestation and morphologically normal foetuses were recorded 20–26 days after RMI-12,936 induced pregnancy termination. These results suggest that in addition to its mid-pregnancy terminating effect, RMI-12,936 is capable of interrupting early pregnancy when given soon after mating in the rat. The safety and efficacy of this compound as a post-coital contraceptive deserves further investigation.