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.

Effects of levonorgestrel on reproductive hormone levels and their receptor expression in Mongolian gerbils (Meriones unguiculatus).

The effects of levonorgestrel (LNG) on serum levels of reproductive hormones and their receptor mRNA expression in the ovary and uterus of Mongolian gerbils were examined. The results show that serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) increased, whereas serum estradiol (E2) and progesterone (P4) decreased profoundly after LNG treatment. LNG down-regulated the mRNA expression of follicle-stimulating hormone receptor (FSHR), luteinizing hormone receptor (LHR), estrogen receptor (ER) ß and progesterone receptor (PR) in the ovary, and ERα and PR in the uterus of Mongolian gerbils. The down-regulated effects were time-dependent and dose-dependent. LNG had no obvious effects on ERα mRNA expression in the ovary. The findings suggest that LNG impairs reproductive hormone receptor expression at the molecular level in Mongolian gerbils. Also, the two ER subtypes may play different roles in the ovary, and ERß may not be the predominant ER subtype in the uterus of Mongolian gerbils. The ovary and uterus may be the important sites of action of LNG through its direct progesterone-like effects in Mongolian gerbils.

Variations in serum gonadotropin and prolactin levels during consecutive reproductive states in Mongolian gerbils (Meriones unguiculatus).

Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL) levels were examined during consecutive reproductive states in Mongolian gerbils. The results indicate that FSH, LH, and PRL levels peak at proestrus, estrus, and diestrus, respectively. During early gestation in primiparous gerbils, gonadotropin levels were the lowest on day 6. This was followed by an increase in FSH and LH levels until days 18 and 15, respectively, with levels remaining constant until day 21. However, in multiparous gerbils, gonadotropin levels were the lowest on day 12 of gestation and were relatively stable between days 15 to 21. In both primiparous and multiparous gerbils, gonadotropin levels increased rapidly from day 21 of gestation to day 3 of lactation, and kept stable between 6-24 days of lactation. PRL peaked during early gestation on days 9 and 6 in the primiparous and multiparous gerbils, respectively, followed by a decline. PRL levels subsequently peaked again on day 21 before parturition. During lactation, PRL levels peaked on days 6 and 9 in primiparous and multiparous gerbils, respectively, followed by a decline until lactation ended. These findings suggest that variations in gonadotropin during the estrous cycle, gestation, and lactation in Mongolian gerbils are similar to those observed in rats, whereas prolactin levels differ. Changes in gonadotropin and prolactin levels during different reproductive states were found to be similar in primiparous and multiparous gerbils, and were correlated with the reproductive stages of Mongolian gerbils.

Variations of serum estradiol and progesterone levels during consecutive reproductive states in Mongolian gerbils (Meriones unguiculatus).

Serum estradiol (E2) and progesterone (P4) levels were measured by chemiluminescence immunoassay (CLIA) during consecutive reproductive states in Mongolian gerbils. The results show that E2 and P4 levels throughout the estrous cycle in Mongolian gerbils peaked at proestrus and estrus, respectively. During gestation in primiparous and multiparous gerbils, E2 levels reached a small peak on day 6 and a maximum peak on day 21, followed by a slight decline until parturition. Thereafter, they dropped sharply during the first 3 days of lactation and remained stable until lactation ended. P4 levels reached a peak on day 12 during gestation in primiparous gerbils, while they peaked on day 6 in multiparous gerbils. The levels of P4 then decreased until parturition. During lactation, P4 levels peaked on day 9 in primiparous gerbils, while they peaked on day 6 in multiparous gerbils, and then the levels declined gradually until lactation ended. The findings suggest that the variations of E2 levels during the estrous cycle, gestation and lactation in Mongolian gerbils are similar to those observed in rats and mice. Changes in E2 levels during different reproductive states were the same in the primiparous and multiparous gerbils, but the variations in P4 levels did not display this tendency. Changing patterns of E2 and P4 levels are suitable for the reproductive stages of Mongolian gerbils.