Stage-Specific Expression Profiles of Anti-Müllerian Hormone and its Type II Receptor in Germ Cells during Spermatogenic Cycle of Rats

Although anti-Müllerian hormone (AMH) is present in seminiferous tubules, its physiological roles in testis remain unclear. We defined expression patterns of AMH and its type II receptor (AMHR2) in germ cells during spermatogenic cycles. To this end, we performed in situ hybridization of Amh and Amhr2, and immunohistochemical staining using antibodies against AMH and AMHR2 in testes from rats aged 10, 15, 21, 35, and 49 days (d). In addition, quantitative RT-PCR analyses were performed to determine relative expression levels of Amh, Amhr2, synaptonemal complex protein 1 (Scp1) and round spermatid basic protein 1 (Rsbn1), and Smads 1, 5, and 8 in germ cells isolated from 49d testes. In 49d testes, synthesis of AMH and AMHR2 corresponded with spermatocyte expression of Amh and Amhr2. Spermatocytes of stages VII-XIV synthesized AMH, and AMH staining was decreased in round spermatids and was not detectable in elongated spermatids. Spermatocytes of stages VII-XIV synthesized AMHR2, and round and elongated spermatids continued expressing AMHR2. The strongest staining of AMH was observed in spermatocytes at stage VIII, and that of AMHR2 was observed in round spermatids at the same stage. When isolated germ cells were cultured with anti-AMH antibody, expression levels of Amh and Amhr2 were significantly increased, those of Smads 1, 5 and Scp1 increased simultaneously, and that of Rsbn1 decreased. We speculate that the AMH-SMADs axis is associated with morphological change from round to elongated spermatids at stage VIII.