Abstract
The aim was to investigate the major C21 steroids produced by spermiating white croaker Micropogonias furnieri (Sciaenidae) in order to establish the potential mediator of gamete maturation in males of this species. The testes steroid production at the spawning season was identified incubating the 3H-17-hydroxy-4-pregnene-3,20-dione precursor through thin layer chromatography, high pressure liquid chromatography, enzymatic oxydation, acetylation and immunochemistry analyses. 17,20β-Dihydroxy-4-pregnen-3-one (17,20β-P) and 11β,17,21-Trihydroxy-4-pregnene-3,20-dione (cortisol) were the main metabolites produced. Contrary to what we expected, 17,20β,21-Trihydroxy-4-pregnen-3-one was not detected. Circulating levels of 17,20β-P were undetectable in immature testes and in those at the first spermatogenesis stages, while a clear increase was observed during the whole spermatogenesis and spermiation phases (from undetectable to 1047 pg mL-1). In vitro studies together with plasma detection suggest that 17,20β-P is a good steroid candidate involved in M. furnieri testes maturation. The role of cortisol during late phases of testes development needs further studies.
Highlights
The role of 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) in several teleost fish has been proven as the oocytes maturation-inducing steroid (MIS) during their final development stages
Taking into account data reported about M. undulatus here we investigated if 17,20β,21-P was produced by M. furnieri spermiating testes
The results demonstrate that 17,20β-P and cortisol are the main metabolites of 17P produced by Micropogonias furnieri spermiating testes
Summary
The role of 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) in several teleost fish has been proven as the oocytes maturation-inducing steroid (MIS) during their final development stages. This role is based on its biological effect mediated by specific receptors and its increased level during the ovulatory surge of luteinizing hormone Lh (Fostier et al, 1973, 1983, 1987; Scott & Canario, 1987; Nagahama & Yamashita, 2008). The 17,20β-P testes synthesis and release in male blood plasma has been studied in more than 100 species as per Scott et al (2010) revision article.
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