title: Induction of germinal vesicle breakdown in Xenopus laevis oocytes: synergistic action of progesterone and insulin.
abstract: Progesterone is the hormone that reinitiates the meiotic division of amphibian oocytes and insulin and insulin-like growth factors are also active on defolliculated oocytes in vitro. We have studied Xenopus laevis oocytes (stage 5-6) of different hormonal sensitivities, obtained from unstimulated and from human chorionic gonadotrophin-stimulated females. Some oocytes from unstimulated females were also precultured with a subthreshold level of progesterone. A dose-dependent potentiating effect of the action of progesterone was observed with insulin, and this was particularly remarkable in low-sensitivity oocytes. Since in the presence of insulin, the optimally effective concentration of progesterone was much reduced (as an example from 1 mumol/1 to 50 nmol/l), it is suggested that an insulin-like growth factor may play a physiological role in the reinitiation of meiosis in ovaries.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D004357:Drug Synergism; D005260:Female; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D009865:Oocytes / Q000187:drug effects*; D011374:Progesterone / Q000494:pharmacology*; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: D006063:Chorionic Gonadotropin; D007328:Insulin; D011374:Progesterone