Effects of Ethynodiol Diacetate (SC 11800) on the Pregnancy and Mating Behavior in Female Rats

Abstract

Effects of ethynodiol diacetate (SC 11800), which has been used for oral contraception as mini-pills, on the estrous cycle, mating behavior and pregnancy were investigated in comparison with those of progesterone, estradiol benzoate and testosterone propionate. When progesterone was administered in a dose of 0.02mg/day for 21 days, the estrous cycle remained almost unchanged, and all treated rats were pregnant soon after mating. When it was administered in higher dose, the female rat showed the vaginal smear of diestrous stage and became infertile as the natural ovulation was inhibited. When estradiol benzoate was administered in the same way, the vagina was swollen like hydrops and the vaginal smear showed estrous stage or quite different stage from it. In a dose of 1 μg/day, the copulation rate did not fall but the pregnancy rate fell markedly. But, in a dose of 10 or 100 μg/day, the copulation and pregnancy rate fell in all the rats treated. When testosterone propionate was administered in a dose of 1 μg/day, the estrous cycle was almost in order and all the rats treated copulated and conceived.