Effects of Gonadotrophins on the Cumulus Oophorus of Isolated Rat Graafian Follicles

Abstract

Graafian follicles were extirpated before the endogenous LH [luteinizing hormone] surge on the day prior to ovulation from PMS [pregnant mare serum gonadotropin] injected immature rats. They were incubated in chemically defined medium in presence or absence of gonadotropins for 4-10 h. After incubation, the oocyte-cumulus complexes were recovered from the follicles and 1 group inspected by Nomarski interference contrast microscopy, and 1 group was placed in saline containing hyaluronidase. In hormone-free medium both the oocyte and the cumulus cells remained morphologically unchanged: a dictyate oocyte surrounded by a compact mass of cumulus cells. Hyaluronidase did not detach cells from the cumulus structure. In presence of LH or FSH [follicle stimulating hormone] morphological changes developed in both cell types: the oocyte resumed meiosis as revealed by germinal vesicle breakdown and polar body formation; the cumulus structure became dispersed and embedded in a viscous matrix. The individual cumulus cells displayed pseudopodia-like processes of the cell surface. Treatment with hyaluronidase resulted in detachment of cells from the cumulus. The effects of LH described on the oocyte and cumulus cells were unimpaired in presence of cyanoketone or aminoglutehimide although these agents blocked the follicular release of progesterone, estradiol and androstenedione as revealed by RIA [radioimmunoassay]. A close functional relationship may exist between the 2 cell types of the cumulus oophorus, the oocyte and the cumulus granulosa cells. Both cell types are affected directly or indirectly by gonadotropins and characteristical changes develop synchronously in both cell types.