Insulin induction of Xenopus laevis oocyte maturation is inhibited by monoclonal antibody against p21 ras proteins.

Microinjection of transforming p21 ras protein induces maturation of Xenopus laevis oocytes, and the induction is blocked by coinjection of monoclonal antibody (Y13-259) against p21 ras proteins. Similar to other inducing agents, the effect of p21 ras protein is mediated via the appearance of maturation or meiosis-promoting factor activity. In addition, the neutralizing antibody markedly reduces oocyte maturation after insulin induction, whereas it fails to inhibit progesterone induction. Our results suggest that insulin induces maturation of oocytes via a different pathway than that of steroidal agents. The induction by insulin is ras dependent, and the action of ras may be directed at the steps before meiosis-promoting factor autocatalytic activation. These results suggest a role of p21 ras protein in the events associated with amphibian oocyte maturation.