Modulation of progesterone-induced Xenopus oocyte maturation by prostaglandins E1 and E2

Prostaglandins E1 (PGE1) and E2 (PGE2), the general local modulators or "local" hormones, were able to inhibit the progesterone-induced maturation of Xenopus oocytes in vitro, but could not induce maturation by themselves. This inhibition was observed on the sensitivity of the maturation process of the oocyte responses to progesterone, but not on the maximum response or responsiveness. The decreased sensitivity of oocytes to progesterone by prostaglandin E1 or E2 was evident in both the increased concentration of progesterone and the prolonged time required for the maturation of 50% of the oocyte. PGE1 and PGE2 did not appear to affect either the basal level or the progesterone-reduced cAMP level of oocytes. Microinjection of PGE1 or PGE2 into the oocytes had no effect on progesterone-induced oocyte maturation, suggesting that other cell surface-mediated signaling events might be responsible for this modulatory effect of the progstaglandins.