Variations in Serum Gonadotropin and Prolactin Levels during Consecutive Reproductive States in Mongolian Gerbils (Meriones unguiculatus)

Abstract

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.