[Anti-mullerian hormone and natural and experimental freemartin effect].

To determine whether anti-Müllerian hormone (AMH) is responsible for the gonadal anomalies observed in bovine female "freemartins" united by placental anastomosis to a male twin, fetal rat and ovine prospective ovaries were exposed to purified bovine AMH in organ culture. We show that AMH reproduces the caracteristical "freemartin effect"; namely the initial inhibition of gonadal and germ cell development, and the differentiation of fetal Sertoli cells forming seminiferous cord-like structures and producing immuno and bioactive AMH. In addition, fetal ovine ovaries submitted to AMH release testosterone instead of estradiol due to an inhibiting effect upon the biosynthesis of their aromatase enzyme. Taken together, these results indicate that AMH is probably the testicular factor responsible for the abnormalities of freemartin gonads and suggest that this hormone could play a pivotal role in normal testis differentiation.