THE ROLES OF FOLLICULAR ENVELOPES IN THE INITIATION OF XENOPUS OOCYTE MATURATION

Gonadotropins and progesterone induce in vitro meiotic maturation of the follicle-enclosed X. laevis oocyte. The kinetics of maturation are identical for both hormones. The enzymatic removal of the follicular envelopes which suppresses gonadotropin activity does not modify the efficiency of progesterone (1 .mu.M)-induced maturation. Defolliculation decreases the kinetic of maturation: GVBD50 (the time necessary to obtain 50% of germinal vesicle breakdown or maturation) was 8.08 .+-. 1.25 h when follicles are induced to mature in the presence of progesterone and 4.30 .+-. 0.89 h in the case of defolliculated oocytes. The follicular envelopes evidently play a role in inhibition of steroid-induced maturation. When oocytes are defolliculated in the presence of aminoglutethimide, an inhibitor of steroid synthesis, the kinetics of oocyte maturation is also decreased (GVBD50: 4.98 .+-. 1.75 h) indicating that the biosynthesis of steroid at the level of follicular envelopes is not involved in the phenomenon.