MICROINJECTED GTP-GAMMA-S INHIBITS PROGESTERONE-INDUCED MATURATION OF XENOPUS OOCYTES

GTP-γ-S inhibits progesterone-induced maturation of Xenopus laevis oocytes and induces a rise in their cAMP levels. GTP-γ-S does not inhibit MPF-induced maturation. Although GTP-γ-S prevents the progesterone-induced increases in protein synthesis and phosphorylation, it has no effect on the basal rates of either. GTP-γ-S also prevents the initial DAG drop induced by progesterone. GDP-β-S effects are ambiguous, but it seems not to affect progesterone-induced maturation. These results suggest that although G-proteins are associated with the pathways affected by progesterone, the effects of progesterone are not mediated by a typical receptor/G-protein/effector interaction. © 1990.