[Implication of progesterone in the resumption of meiosis of rat follicular ova (author's transl)].
Gonadal steroids induced by ovulatory stimuli may be among the factors regulating resumption of meiosis even in mammals. Possible role of progesterone on the resumption of meiosis was studied by examining the effects of neutralization of endogenous progesterone induced by an ovulatory dose of hCG with rabbit antiserum to progesterone (anti-P) on oocyte maturation in rats. Immature rats received subcutaneous injection of 5 IU PMS on day 22 followed by intravenous injection of 10 IU hCG 56 hrs later. Animals were sacrificed 6 hrs after hCG injection and number of oocytes with or without germinal vesicle breakdown was counted on serial sections of both ovaries. Treatment with anti-P induced a marked decrease in incidence of meiosis of follicular ova in large (greater than 250 microns in diameter), but no appreciable change occurred in intermediate follicles (125-250 microns in diameter). With the replacement of exogenous P, percent incidence of resumption of meiosis recovered significantly, but not completely, in large follicles compared to those in the control group. The results can be interpreted as indicating the conversion of progesterone into estrogen which may exert the partial inhibition on meiosis by estrogen. When the replacement of exogenous P was supplemented with the simultaneous injection of antiserum to estrone to neutralize endogeneous estrogen, a complete recovery of resumption of meiosis in large follicles was observed. The present results suggest that the hCG-induced preovulatory progesterone has a localized facilitating effect on the resumption of meiosis of oocytes, predominantly in the large follicles of rats.
D000818:Animals; D006063:Chorionic Gonadotropin / Q000502:physiology; D004967:Estrogens / Q000502:physiology; D005260:Female; D007106:Immune Sera / Q000494:pharmacology; D008540:Meiosis / Q000187:drug effects*; D009865:Oocytes / Q000187:drug effects; D010060:Ovulation / Q000187:drug effects*; D010063:Ovum / Q000187:drug effects; D011374:Progesterone / Q000276:immunology / Q000494:pharmacology / Q000502:physiology*; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains
D006063:Chorionic Gonadotropin; D004967:Estrogens; D007106:Immune Sera; D011374:Progesterone