[On the effect of an oocyte factor on the formation of cumulus oophorus in human antral follicles].

The possible existence of a granulosa cell growth factor (GGF) in the oocyte was investigated by using the mitotic index (%) of granulosa cells (GC) in human antral follicles. 50 follicles (0.4-13 mm in diameter) in 35 ovaries obtained from 35 women were used for the experiments. In each follicle, GC were divided into two groups, cumulus and mural GC, according to the distance from the oocyte. The following results were obtained: The Mitotic Index (MI) of cumulus GC was 8.2 +/- 0.5 (M +/- SE) and was two fold higher than that of mural GC, 4.7 +/- 0.4 (p less than 0.001). As follicles developed, MI of mural GC increased until their diameter reached 3mm but beyond 3mm, MI decreased. On the other hand, there was little relationship between MI of cumulus GC and the follicular size, and MI was constantly high in value. MI of both cumulus and mural GC was higher in the late follicular phase than in other phases of the cycle. These results suggest that the proliferation of GC in growing follicle might be regulated by some unknown substance (GGF) secreted from the oocyte as well as the endocrinological environment. It is also suggested that the presence of the oocyte plays a crucial role in the cumulus oophorus formation in the antral follicles.