The role of C-type natriuretic peptide in rat testes during spermatogenesis.

C-type natriuretic peptide (CNP) is a 22-amino acid peptide and act as a local paracrine or autocrine regulator. There is growing evidence that CNP is involved in male reproductive processes. To investigate the role of CNP during spermatogenesis, we measured the mRNA expression of CNP and its specific membrane-bound natriuretic peptide receptor-B (NPR-B) using real-time RT-PCR in the testes of normal rats on different postnatal days. After that spermatogenesis dysfunction model induced by ornidazole was established with the aim to study the correlation of CNP with spermatogenic dysfunction. Then, Sertoli cells from 18- to 22-day-old healthy male rats were cultured in the presence of different CNP concentrations (1×10(-6), 1×10(-7) and 1×10(-8) mol l(-1)), and the mRNA expression levels of androgen-binding protein, inhibin B and transferrin were examined at 0 min, 30 min, 1 h, 2 h, 4 h, 8 h, 12 h, 24 h and 48 h. During the postnatal development of rat testes, the highest mRNA expression levels of CNP and NPR-B were found at postnatal D(0), and the levels then declined gradually, with a second CNP peak at postnatal D(35). In the ornidazole-induced infertile rat testes, CNP gene expression was lower than in the uninduced rats (P<0.05), while NPR-B gene expression was greater (P<0.05). In cultured Sertoli cells, supplementation with CNP stimulated the gene expression of androgen-binding protein/inhibin B/transferrin, particularly at 12 h, and 1×10(-7) mol l(-1) CNP had the highest upregulation effect. The gene expression levels of CNP/NPR-B in rat testes at different postnatal stages and in infertile rat testes indicated that CNP may participate in the physiology and/or pathology related to spermatogenesis. Moreover, CNP regulated endocrine function in Sertoli cells. Taken together, these results showed that CNP is closely tied to spermatogenesis.