Involvement of cAMP in inhibition of maturation of follicle-enclosed oocytes by actinomycin D in Xenopus laevis and Rana temporaria

Abstract

Production of estradiol-17 beta and cAMP was assayed during maturation of the follicle-enclosed oocytes of Xenopus laevis and Rana temporaria stimulated by pituitary suspension or hCG, correspondingly. In some samples, the nuclear function was suppressed by pretreatment with AD. The level of estradiol-17 beta in the oocytes of the both species was very low and was not affected by hormonal or AD treatment, while the level of cAMP (follicle+medium) increased. When maturation was stimulated by low concentrations of gonadotropic hormones inducing complete or near 100% maturation, the cAMP level increased 1.4- to 3.9-fold. Both higher concentrations of the gonadotropic hormones and pretreatment of the follicles with AD increased the cAMP level still more. Combination of these treatments led to a greater increase of cAMP and to inhibition of oocyte maturation. We conclude that cAMP, rather than estradiol-17 beta, is involved in the AD-induced inhibition of amphibian oocyte maturation stimulated by gonadotropins.