EXPRESSION OF INHIBIN ALPHA-SUBUNIT AND BETA(A)-SUBUNIT MESSENGER-RNAAND PROTEIN IN THE FETAL SHEEP OVARY THROUGHOUT GESTATION

In adult sheep, inhibin expression in developing follicles appears to be associated with antrum formation. Our objective was to investigate using in situ hybridization and immunohistochemistry whether antral fo llicles present before birth in the sheep expressed mRNA or peptide fo r inhibin alpha- and beta(A)-subunits. At days 70 and 100 when only pr imordial and primary follicles were present, there was no detectable m RNA or peptide for either inhibin subunit. By days 130 and 140 (term = 145 days), many secondary follicles were present, a proportion of whi ch (similar to 50%) expressed detectable levels of alpha-subunit mRNA but not peptide. A number of antral follicles were present by this sta ge, all of which expressed alpha-subunit mRNA and peptide. Expression of beta(A)-subunit mRNA and peptide was undetectable at all. stages of gestation. Our results indicate that even in non-ovulatory follicles present before birth, expression of inhibin, at least the alpha-subuni t, is developmentally linked with antrum formation.