PROSTAGLANDIN PRODUCTION BY THE LARGEST PREOVULATORY FOLLICLES IN THE DOMESTIC HEN (GALLUS-DOMESTICUS)

An injection of 5 μg of gonadotropin-releasing hormone (GnRH) into hens 8 h prior to oviposition advanced the expected time of oviposition by approximately 1h. The plasma concentration of progesterone increased approximately 1 h earlier in GnRH-inecjected hens in comparison to saline-injected hens. The plasma concentration of 13,14-dihydro-15-keto-prostaglandin F(2α) (PGFM) increased significantly (p < 0.05) at the time of oviposition in both the GnRH- and saline-injected hens. Significantly (p < 0.05) greater concentrations of prostaglandin F(2} (PGF(2α)) were assayed in media containing the largest preovulatory follicles collected at oviposition than in media containing the second and fifth largest preovulatory follicles collected at the same time. No prostaglandin was detected in media containing small, nonhierarchial follicles. The concentration of PGF(2α) in media containing granulosa cells from the largest preovulatory follicle was significantly greater (p < 0.05) than in media containing 4 times as many theca cells. Ovine luteinizing hormone (oLH) alone or in combination with arachidonic acid had no effect on PGF(2α) output from granulosa cells collected 6 h before oviposition, whereas A23187 caused a small stimulation of PGF(2α) output. However, treating cells first with oLH and then with A23187 stimulated a 15- to 20-fold increase in PGF(2α). None of these stimuli enhanced the already high output of PGF(2α) when added to incubations of granulosa cells collected within 5 min after oviposition. These data suggest that the granulosa cells of the largest preovulatory follicle are the major intraovarian source of prostaglandin and that production of PGF(2α) is associated with the preovulatory surges of gonadotropins and steroid hormones preceding oviposition.