Control mechanisms of fish spermatogenesis and early oogenesis by steroid hormones
2008
Miura, T.(Ehime Univ., Ainan (Japan). South Ehime Fisheries Research Center)
Fish spermatogenesis is controlled by the sex steroid hormones. Mitotic divisions of spermatogonia can categorized by spermatogonial stem cell renewal and spermatogonial proliferation toward meiosis. Spermatogonial renewal is regulated by estradiol-17 beta (E2) and spermatogonial proliferation toward meiosis is promoted by 11-ketotestosterone (11-KT). The action of E2 and 11-KT is mediated by other factors produced by Sertoli cells; E2 is mediated by spermatogonial stem-cell renewal factor and 11-KT is mediated by spermatogenesis preventing substance (anti-Muellerian hormone: AMH) and activin B. Meiosis is induced by 17alpha, 20beta-dihydroxy-4-pregnen-3-one (DHP), which is progestin in teleost. In oogenesis, DHP also initiate meiotic prophase. After spermiogenesis, immature spermatozoa undergo sperm maturation. Sperm maturation is also regulated by DHP. The DHP acts directly on spermatozoa to active the carbonic anhydrase existed in the spermatozoa. This enzymatic activation causes an increase in the seminal plasma pH, enabling spermatozoa to motile.
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