Alphafetoprotein and atretic follicles in the ovary of the pregnant rat.

Previous experiments have been conducted concerning the role of alphafetoprotein in genital system blockade in several cases: during adult rat N2-fluorenylacetamide hepatocarcinogenesis, after alphafetoprotein injections into normal adult female rats, during fetal life, and during postnatal and prepuberal development. In these conditions, alphafetoprotein is present at high plasma levels, and the normal cyclic ovarian function is stopped or nonexistent. The degenerating oocytes observed in the ovaries are often AFP-positive by histo-immunolocalization. Pregnancy corresponds to a physiological state in which alphafetoprotein levels are high while the gonadal activity is not characterized by ovulatory cycles. In order to assess our hypothesis, alpha-fetoprotein was studied in the ovary of pregnant rats from day 18 to 21 of gestation by an immunofluorescent technique, and alpha-fetoprotein was assayed in plasma samples. The results of this work show that, during pregnancy, follicular maturation is blocked at the antral stage, and the follicles contain degenerating oocytes that are AFP-positive in immunofluorescence. In conclusion, we suggest that the alpha-fetoprotein produced by the fetal liver and the yolk sac is disseminated in the amniotic fluid and passes through the placenta, and then reaches the ovarian follicles and the oocytes. The possible role of alphafetoprotein in follicular atresia is discussed.