Acrosin-binding protein (ACRBP) in the testes of stallions.

Acrosin Binding Protein (ACRBP) is specifically localized in the acrosome of germ cells of several species, including mice, pigs, guinea pigs, and humans. The main objective of this study was to investigate ACRBP patterns in the germ cells of stallions at different reproductive stages and seminiferous tubule stages using Western blot, immunohistochemistry, and immunocytochemistry techniques. The stallion reproductive stages were classified as follows: pre-pubertal and post-pubertal stages based on the presence/absence of lumen opening in the seminiferous tubules and full spermatogenesis. The protein band associated with the presence of ACRBP appeared at approximately 35-kDa position, indicating that the antibody used in this study recognizes the mature form of ACRBP. During the pre-pubertal stages, immunolabeling did not detect the presence of ACRBP in the germ cells. However, during the post-pubertal stage, immunolabeling of the ACRBP was observed in the pachytene spermatocyte as well as for round, elongating, and elongated spermatids, and in some spermatozoa. In conclusion, the ACRBP can be used as a molecular marker for pachytene spermatocytes, and for round, elongating, and elongated spermatids. The ACRBP can be used to monitor either normal spermatogenesis in the testicular tissues, or germ cell development in vitro. Because the ACRBP is present in the germ cells of stallions that have undergone puberty, it can be used as an indicator for the sexual maturation of stallions.