ADVANCES IN OBSTETRICS AND GYNECOLOGY

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Gonadal steroids induced by ovulatory stimuli may be among the factors regulating resumption of meiosis even in mammals. Possible role of estrogen on the resumption of meiosis was studied by examining the effects of neutralization of endogenous estrogen induced by PMS alone or in combination with hCG with rabbit antiserum to estrone (anti-E).
Immature rats received subcutaneous injection of 5 IU PMS alone or sequentially in combination with intravenous injection of 10 IU of hCG.
Treatment with PMS alone induced no appreciable change 74hr later in the incidence of meiosis but intravenous injection of anti-E increased significantly the incidence in meiosis of follicular ova in intermediate and large follicles. Sequential treatment with PMS and hCG increased markedly the incidence of meiosis 6 and 18hr after hCG. Simultaneous injection of anti-E with hCG induced a significant increase in incidence of meiosis of follicular ova in intermediate but not in large follicles 6hr after hCG. However, the incidence of meiosis increased in both intermediate and large follicles 18hr after hCG.
It is suggested that hCG induced preovulatory estrogen has a intraovarian inhibitory effect on the resumption of meiosis of follicular ova predominantly in intermediate follicles counteracting the meiosisinducing action of hCG

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