[Role of progesterone in the ovulatory process of PMSG/hCG treated immature female rats].
To determine exactly when progesterone (P) acts as a most important mediator in the ovulatory process, a dose of 10mg/kg of RU486, an antiprogesterone, was administered to PMSG/hCG treated immature female rats (22 days old) at 0 (RU0 groups), 2 (RU2 group), 4,6,8 or 10 hours after an hCG injection, respectively. In the RU0 groups, the ovulatory effect of P was investigated at 0.2 (P2 group), 4 (P4 group), 6 or 8 hours after the hCG injection. Ovulation rates were calculated 24 hours after the hCG injections. Serum P and estradiol (E2) concentrations in the RU0 groups, the P2 group and the control rats (C group), were determined. The results were as follows. 1) The numbers of ova in the RU0, RU2 and RU4 group rats were significantly (p less than 0.01, p less than 0.01 and p less than 0.01) lower than that in the C group rats. 2) In the P2 and P4 groups, the numbers of ova were significantly (p less than 0.01 and p less than 0.01) increased compared with the RU0 group and returned to the control range. 3) In the RU0 group, the serum P and E2 concentrations within 8 hours after an hCG injection did not show any significant differences compared with the C group. In contrast, in the P2 group, the P concentrations at 4 and 6 hours after hCG increased significantly (p less than 0.01 and p less than 0.01) compared to the corresponding RU0 group. These results clarified an indispensable role of P in the ovulatory process within 6 hours after an hCG injection.
Iwamasa
J
J
Department of Obstetrics and Gynecology, Kumamoto University Medical School.
Tajima
C
C
Matsuura
K
K
Okamura
H
H
D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D004958:Estradiol / Q000097:blood; D005260:Female; D006064:Gonadotropins, Equine / Q000494:pharmacology*; D015735:Mifepristone / Q000494:pharmacology; D010060:Ovulation / Q000187:drug effects; D011374:Progesterone / Q000097:blood / Q000494:pharmacology / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D006063:Chorionic Gonadotropin; D006064:Gonadotropins, Equine; D015735:Mifepristone; D011374:Progesterone; D004958:Estradiol