抄録
In ovariectomized rats, daily injections of 2mg of 17α-ethinyl-19-nortestosterone induced vaginal estrus (vaginal index, 5) continuing for several days. But after this, vaginal indices fell rapidly and animals came into anestrous state. Subsequently, however, indices rose gradually again up to 5 (full estrus). Smaller doses of the steroids (0.125 and 0.5mg daily) invariably led to continuous estrus, interruption failing to occur. The sequence of events is quite comparable to that occurring in ovariectomized rats receiving daily injections of 2mg progesterone and 0.125mg estrone concurrently (Maekawa, 1955). It seems highly probable, therefore, that progestational property of 17α-ethinyl-19-nortestosterone interferes with estrogenic action of the same steroid as progesterone prevents the effects of estrogen administered simultaneously.
