A possible role of prostaglandin F-2 alpha in the development of ovarian follicles in guinea-pigs.
Uterine PGF-2 alpha in the guinea-pig was eliminated by hysterectomy on Day 9 of the oestrous cycle and an increasing period of reduced PGF-2 alpha availability to the ovary was created by deferring replacement therapy with PGF-2 alpha from Day 9 to Day 11, 13 and 15. Ovulation, observed in 94% of the animals, was inevitably delayed. The treatment cycle length was progressively extended from the normal 15--16 days to 19--21 days. Similar results were obtained if endogenous PGF-2 alpha was suppressed by indomethacin injection instead of removing the uterus. That ovulation had been delayed and not occurred from more recently recruited follicles was evident from the total absence of atretic follicles of the expected size had they become atretic due to the lack of PGF-2 alpha at some critical time between Days 9 and 15. Pituitary homogenate and hCG injected on Day 16 shortened the PGF-2 alpha treatment cycle by 2 days, but stimulated ovulation in only 42% of the animals. When endogenous PGF-2 alpha was eliminated by hysterectomy and daily injections of indomethacin, follicular development ceased at approximately 0.8 mm instead of the 1.0 mm diameter found just before the preovulatory LH surge. It is suggested that (1) PGF-2 alpha has to act on developing follicles for a given period before they are capable of ovulation, and (2) that PGF-2 alpha is one of the factors required to stimulate the growth of the Graafian follicles at the end of the oestrous cycle.
D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D015237:Dinoprost; D004971:Estrus / Q000187:drug effects; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D006168:Guinea Pigs; D007044:Hysterectomy; D007213:Indomethacin / Q000494:pharmacology; D006080:Ovarian Follicle / Q000187:drug effects / Q000254:growth & development*; D010060:Ovulation / Q000187:drug effects; D011247:Pregnancy; D011460:Prostaglandins F / Q000494:pharmacology / Q000502:physiology*
D006063:Chorionic Gonadotropin; D011460:Prostaglandins F; D005640:Follicle Stimulating Hormone; D015237:Dinoprost; D007213:Indomethacin