REQUIREMENT OF ZN2-LAEVIS( FOR THE OOCYTE MATURATION INDUCED BY PROGESTERONE IN XENOPUS)

We report for the first time that o-phenanthroline, a Zn2+-chelating a gent, inhibits the induction of meiotic maturation of Xenopus laevis o ocytes by progesterone, suggesting that a Zn2+-dependent process is a prerequisite for the initial step. o-Phenanthroline also inhibited the maturational response induced when the external medium was artificial ly supplemented with Zn2+, which is capable of inducing oocyte maturat ion in the absence of progesterone. Also, oocyte maturation induced by Zn2+ was inhibited by both Ca2+, Mg2+-free medium and cycloheximide, an inhibitor of protein synthesis. In addition, comparable changes hav e been observed in oocytes with progesterone and Zn2+, with a similar time course of oocyte maturation. It is concluded that intracellular Z n2+ in addition to Ca2+ and Mg2+ may play a physiological role(s) in r egulating the oocyte maturation process in Xenopus laevis.