Response of mouse ovaries in vivo and in organ culture to pregnant mare's serum gonadotrophin and human chorionic gonadotrophin.

Abstract

Summary. A series of experiments was carried out to assess the effects of HCG in vivo and in organ culture on oocyte and follicle maturation following treatment with PMSG in vivo. Quantitative histological procedures were used to assess the proportion of follicles in which the oocytes had resumed meiosis beyond the germinal vesicle (diffuse diplotene) stage in response to different doses of hormones. The injection of 3 to 5 i.u. PMSG followed 48 hr later by treatment with 1 to 2 i.u. HCG induced the maximum preovulatory response in ovaries of Schofield albino mice both in vivo and in organ culture. The proportion of large antral follicles with oocytes at metaphase II, however, was much lower in culture than in the intact animal. By contrast, the number of pre-antral and small Graafian follicles increased to a level far higher than in vivo and thus the overall total number of oocytes that progressed beyond the germinal vesicle stage was higher in organ culture.