Testicular concentration of meiosis-activating sterol is associated with normal testicular descent

In the cryptorchid stallion, spermatogenesis is arrested at various levels before the completion of meiosis. In men, infantile cryptorchidism is also often associated with oligo- and azoospermia during adulthood. An impairment of spermatogenesis might be reflected in the level of locally produced factors. Formerly, a meiosis-activating sterol (T-MAS) has been isolated in murine and bovine testes. This sterol possesses the potential to trigger resumption of meiosis in cultured mouse oocytes, indicating that it might play an important role in the regulation of the meiotic process in the female gamete. The function of T-MAS in the testis is still unclear, but T-MAS may be associated with spermatogenesis. The objectives of this study were 1) to demonstrate the presence of T-MAS in equine testes, 2) to compare the contents of T-MAS in testicular tissue of stallions with complete and incomplete testicular descent and 3) to compare testicular T-MAS concentration before and after puberty Testes were collected from 16 normal and cryptorchid stallions submitted for castration and stored at -80 degrees C until the content of T-MAS was measured quantitatively with an HPLC-assay. In stallions > or = 2 years of age, the content of T-MAS was higher (P < 0.001) in normal testes (19.3+/-1.1 microg T-MAS/g, n=7) than in inguinally (4.1+/-2.4 microg T-MAS/g, n=4) or abdominally located testes (1.6+/-0.2 microg T-MAS/g, n=2). The contents of T-MAS in normal testes from stallions < 2 years of age (2.8+/-1.5 microg T-MAS/g, n=4) was lower than in normal testes from stallions > or =2 years of age (P < 0.001) From the present study it can be concluded that T-MAS is present in equine testicular tissue. Furthermore, the present study demonstrates that the production of T-MAS in testicular tissue is, concurrently with spermatogenesis, associated with normal testicular descent and is temporarily related to the onset of puberty.