We have investigated the effect of administration of human chorionic gonadotrophin (hCG) to immature female rats pretreated with pregnant mare serum gonadotrophin (PMSG) on ovarian inhibin α-subunit mRNA serum inhibin and circulating gonadotrophin levels. PMSG stimulation alone caused a 5-fold increase in relative inhibin a-subunit mRNA levels and a 12-fold increase in serum inhibin by 48 h. However injection of hCG at 40 h suppressed PMSG-stimulated ovarian inhibin a-subunit mRNA and serum inhibin to levels at 48 h not statistically significantly different from controls. Serum follicle-stimulating hormone (FSH) fell after PMSG treatment but rose after combined PMSG-hCG treatment. Serum luteinizing hormone (LH) was unchanged after PMSG alone but also rose after combined PMSG and hCG therapy. In conclusion hCG suppresses ovarian inhibin synthesis in PMSG-stimulated immature female rats with preservation of the reciprocal relationship between inhibin and FSH. This immature female rat model therefore provides further insight into the effects of LH or hCG on granulosa cell inhibin production just prior to ovulation.
- Gene expression
- Human chorionic gonadotropin
- Pregnant mare serum gonadotropin