ANTI-MULLERIAN HORMONE AND ANTI-MULLERIAN HORMONE TYPE-II RECEPTOR MESSENGER-RIBONUCLEIC-ACID EXPRESSION DURING POSTNATAL TESTIS DEVELOPMENT AND IN THE ADULT TESTIS OF THE RAT

Anti-mullerian hormone (AMH) induces degeneration of the mullerian duc ts during male sex differentiation and may have additional functions c oncerning gonadal development. In the immature rat testis, there is a marked developmental increase in AMH type II receptor (AMHRII) messeng er RNA (mRNA) expression in Sertoli cells, concomitant with the initia tion of spermatogenesis. AMHRII mRNA is also expressed at a high level in Sertoli cells in adult rats. To obtain information about the possi ble functions of AMH in the testis, we investigated the postnatal expr ession patterns of the genes encoding AMH and AMHRII in the rat testis in more detail. Using RNase protection assays, AMH and AMHRII mRNA ex pression was measured in total RNA preparations from testes or testicu lar tubule segments isolated from control rats and from rats that had received various treatments. The testicular level of AMHRII mRNA was f ound to be much higher than that of AMH mRNA in adult rats. AMH mRNA w as detected at a maximal level at stage VII of the spermatogenic cycle and at a low level at the other stages. AMHRII mRNA increases from st age XIII, is highest at stages VI and VII, and then rapidly declines a t stage VIII to almost undetectable levels at stages IX-XII. It was fo und that the increase in testicular AMHRII mRNA expression during the first 3 weeks of postnatal development also occurs in sterile rats (pr enatally irradiated), and hence, is independent of the presence or abs ence of germ cells. Yet, the total testicular level of AMHRII mRNA was decreased in sterile adult rats (prenatally irradiated or experimenta l cryptorchidism), as compared with intact control rats. However, trea tment of adult rats with methoxyacetic acid or hydroxyurea, which resu lted in partial germ cell depletion, had no effect on total testicular AMHRII mRNA expression. We conclude that a combination of multiple sp ermatogenic cycle events, possibly involving changes of Sertoli cell s tructure and/or Sertoli cell-basal membrane interactions, regulate aut ocrine AMH action on Sertoli cells, in particular at stage VII of the spermatogenic cycle.