[Promoting effect of oocytes and FSH on the growth of follicles].

Immature follicles grow autonomously even without pituitary gonadotropins. In order to explore this reason, promoting effects of oocyte and some endocrinological substances on the proliferation of granulosa-cells (G-cells) have been investigated using the labelling index (LI) with 3H-Thymidine (3H-Tdr) and mitotic index (MI) in mature mice and immature hypophysectomized (hypox) rats. The following results were obtained: In preantral follicles with the oocyte diameter below 69 mu, the LI was low (9.5 +/- 1.7%) (m +/- SE) and the follicular diameter was small (69.0 +/- 7.7 mu). As the oocyte developed with its diameter 80-89 mu, the LI increased (20.3 +/- 3.8%) and the follicular diameter also increased (192.3 +/- 19.4 mu). In preantral follicles with the oocyte diameter over 80 mu the G-cells near the oocyte had a much higher LI than the distant G-cells. After the antrum formation, the LI and MI of cumulus layers adjacent to the oocyte were three times higher than those of mural layers. Among the mural cell layers in the antral follicle, the layer adjacent to the antrum showed remarkably high LI in comparison with the distant layers. In FSH primed group the LI of G-cells was two fold higher than that in hypox control group (p less than 0.001). In the preantral follicle of hypox control group the G-cells near the oocyte had a much higher LI than the distant G-cells. Moreover in FSH primed group the LI indicated high value not only in the cell layers adjacent to the oocyte but also in the cell layers adjacent to the theca interna. In LH, E2 and P4 primed groups the LI of G-cells had no change significantly in comparison with that in hypox control group. In FSH + LH primed group the LI of G-cells decreased significantly in comparison with that in FSH primed group (p less than 0.05). In FSH + E2 group the LI had no change significantly in comparison with that in FSH primed group. These results suggest that the granulosa-cell growth factor (GGF) in oocyte, which seems to play a role in the formation of cumulus, is secreted with the growth of the oocyte. In antral follicles the GGF is transported through the follicular fluid.(ABSTRACT TRUNCATED AT 400 WORDS)