EFFECT OF ANTI-MULLERIAN HORMONE ON SERTOLI AND LEYDIG-CELL FUNCTIONSIN FETAL AND IMMATURE RATS

Anti-Mullerian hormone (AMH) is mainly involved in the regression of M ullerian ducts in male fetuses, but it may have other functions linked to gonadal development. The present study examines the effect of AMH on steroidogenesis by Sertoli and Leydig cells in fetal and immature r ats during the period where AMH is physiologically produced in the tes tis. The basal aromatase activity of Sertoli cells in primary culture was strongly stimulated (77-91%) by cAMP. AMH (35 nra) reduced cAMP-st imulated aromatase activity by 49-69% as early as fetal day 16 and unt il postnatal day 20. This effect was dose dependent and was seen after 48 h in culture. AMH also blocked the Sertoli cell aromatase activity stimulated by FSH, but LH did not stimulate this activity, confirming that the aromatase activity effectively resulted from Sertoli cells a nd not from contaminating Leydig cells. RT-PCR analysis showed that AM H reduced aromatase activity by decreasing the amount of aromatase mes senger RNA. AMH also inhibited the LH-stimulated testosterone producti on by dispersed fetal Leydig cells in culture in a dose-dependent mann er. The inhibitory effect of AMH did not depend on the fetal stage stu died (16 or 20 days postconception) and resulted from a drop in the st eroidogenic activity of each Leydig cell without affecting the number of 3 beta-hydroxysteroid dehydrogenase-positive cells. These data prov ide the fir st evidence that AMH, like other members of the transformi ng growth factor-beta family, has an autocrine/paracrine effect on tes ticular steroidogenic function during the fetal and prepubertal period s.