INHIBITORY ACTION OF FOLLICULAR-FLUID ON PROGESTERONE AND PROSTAGLANDIN SYNTHESIS IN BOVINE FOLLICLES

The present studies examined the inhibitory effect of mid-cycle and preovulatory bovine follicular fluid (bFF) on the secretion of progesterone and prostaglandin F(2α) (PGF(2α)) by bovine theca and granulosa cells cultured in tissue culture Medium 199. The inhibitory effect of bFF on the secretion of PGF(2α) by incubated and cultured hemipituitary glands of male rats was also studied. Addition of 5, 10 or 20% charcoal-extracted, mid-cycle bFF to the culture medium caused a twofold decrease in the accumulation of both progesterone and PGF(2α) by the cultured granulosa cells (P<0.01). In contrast, when preovulatory bFF was used, there was no inhibitory effect on secretion of progesterone and PGF(2α). The addition of 10% mid-cycle bFF to the culture medium caused a two- to fourfold decrease in the accumulation of both PGF(2α) and progesterone by the cultured theca (P<0.008). However, in the presence of 1 μg LH/ml, the inhibitory effect of mid-cycle bFF on progesterone and PGF(2α) secretion was abolished. The secretion of PGF(2α) was significantly (P<0.03) decreased in male rat hemipituitary glands after 5 h of incubation or 18 h of culture. These findings suggest that bFF from mid-cycle follicles inhibits prostaglandin synthetase as well as luteinization. The inhibition disappeared with bFF from preovulatory follicles.