Regulation of the inducible form of prostaglandin endoperoxide synthase in the perfused rat ovary

(CA), previously shown to reversibly inhibit ovulation in the in v'rtro perfused rat ovary. Preovulatory ovaries were perfused for 7 h, and soluble extracts from granulosa cells and residual ovarian tissue were obtained for immunoblotting and determination of the tissue contents of PGS-1 /PGS-2. The tissue concentrations of prostaglandins (PGE2, PGF2a and 6-keto-PGF1a) were measured. The ovaries were perfused with medium alone (control) or medium containing LH (0.1 ug/ml) and IBMX (0.2 mM), LH + IBMX + CA (10 ug/ml) or LH + IBMX + CA + progesterone (10 ug/ml). PGE2, PGF2a and 6-keto-PGF1a tissue concentrations were increased by LH + IBMX, with highest values detected for PGE2. The addition of CA alone or CA in combination with exogenous progesterone, did not change the values of prostaglandins increased by LH + IBMX. The content of PGS-1 was only marginally changed in both granulosa cells and residual ovarian tissue in the different treatment groups, compared to the control group. In contrast, PGS-2 was markedly increased by LH + IBMX, especially in the granulosa cells. The addition of CA, in combination with LH + IBMX, resulted in a small decrease of PGS-2, and progesterone further decreased its content. In the residual ovarian tissue, only minor changes of PGS-2 were detected. These results demonstrate that LH and progesterone selectively regulate the expression of PGS-2 in rat granulosa cells, whereas the hormonal regulation of PGS-1 is less pronounced. Progesterone inhibits PGS-2 in granulosa cells but has negligible effects on the total ovarian synthesis of