Evidence that androgens are the primary steroids produced by Xenopus laevis ovaries and may signal through the classical androgen receptor to promoteoocyte maturation

Steroid-induced maturation of Xenopus oocytes has long served as a model fo r studying meiosis. Progesterone has been considered the relevant steroid c ontrolling maturation, perhaps through interactions with classical progeste rone receptors. In this study, we provide evidence that androgens, rather t han progesterone, are the physiologic mediators of Xenopus oocyte maturatio n. Androgens were equal or more potent activators of maturation in vitro re lative to progesterone and were significantly more abundant in the serum an d ovaries of beta -human chorionic growth hormone-stimulated frogs. Androge n action appeared to be mediated by classical androgen receptors (ARs) expr essed in oocytes, as androgen-induced maturation and signaling was specific ally attenuated by AIR antagonists. Interestingly, we found that progestero ne was rapidly converted to the androgen androstenedione in isolated oocyte s by the enzyme CYP17, suggesting that androgens may be promoting maturatio n even under conditions typical for "progesterone-mediated" maturation assa ys. Androgens are thought to play an important role in ovarian development as well as pathology, and signaling through the AR may prove to be a major regulatory mechanism mediating these processes.