Effects of quinestrol as a contraceptive in mongolian gerbils (Meriones unguiculatus).

The contraceptive effects of quinestrol in Mongolian gerbils were examined. The results showed that body weight significantly increased after quinestrol treatment, except in the group that received the highest dose. The gonadosomatic index of ovaries decreased, whereas that of uteri increased, and uterine edema appeared after quinestrol treatment. Histological examination revealed that the ovaries had a lack of mature follicles and corpora lutea and that the myometrium and endometrium of the uteri became thin after quinestrol treatment. Persistent estrous appeared after quinestrol treatment, and time to persistent estrous shortened with increasing doses of quinestrol. Serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels decreased, whereas estradiol (E2) and progesterone (P4) levels increased after quinestrol treatment, and the effects were dose-dependent. During gestation, the serum E2 levels in the different treatment groups were not significantly different. During gestation in the control groups, the serum P4 levels from days 0 to 15 were higher than in the quinestrol-treated groups; however, they did not show significant differences from days 18 to 24. Doses of 0.1 to 2.7 µg/g quinestrol over 6 days completely inhibited fertility. Birth time was prolonged with increasing doses of quinestrol. The findings suggest that quinestrol has marked estrogenic effects in Mongolian gerbils and may inhibit follicle maturation and ovulation through lowered gonadotropin levels. Uterine edema and abnormal E2 and P4 levels during gestation are important causes of pregnancy failure in quinestrol-treated Mongolian gerbils. Quinestrol causes prolonged inhibition of fertility in Mongolian gerbils.