Studies on oocyte maturation of the medaka,Oryzias latipes. VIII. Role of follicular constituents in gonadotropin- and steroid-induced maturation of oocytes in vitro

✍ Scribed by Iwamatsu, Takashi

• Publisher: John Wiley and Sons
• Year: 1980
• Tongue: English
• Weight: 719 KB
• Volume: 211
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402110212

✦ Synopsis

Abstract

Participation of the follicular constituents in gonadotropin‐ and steroid‐induced maturation of Oryzias latipes oocytes was examined in vitro by removing these constituents and coculturing them with the denuded oocytes. Removal of all follicular constituents prevented gonadotropin‐induced maturation of oocytes, but the removal of the thecal cells and the basal lamina from the follicle did not prevent maturation. Moreover, the denuded oocytes did mature in the presence of gonadotropin when cocultured with granulosa cells previously separated from large preovulatory follicles or with postovulatory follicles. However, the denuded oocytes did not respond to gonadotropin by maturing when cocultured with either thecal cells and basal lamina of the, premature follicles or the granulosa cells of small follicles 22–24 hr before ovulation. These results indicate that the presence of the granulosa cells of large pre‐ and postovulatory follicles is important for gonadotropin‐induced oocyte maturation. The denuded oocytes, which were incapable of responding to gonadotropin, were stimulated by various steroids to undergo meiotic maturation. The concentrations of steroids effective in inducing maturation were lower for the denuded oocytes than for the oocytes within intact follicles or enveloped by granulosa cells alone.

The present results suggest that the gonadotropin‐stimulated granulosa cells of both pre‐ and postovulatory follicles play a major role in inducing oocyte maturation through secretion of steroids in the circadian ovulatory cycle of Oryzias latipes.