In vitro steroidogenesis of the gonads of the protogynous Pacific wrasse, Haliochoeres trimaculatus
Abstract:Testicular and ovarian fragments of the protogynous Pacific wrasse Haliochoeres trimaculatus were incubated in vitro with [3H]pregnenolone ([3H]P5), [3H]17-hydroxyprogesterone ([3H]17OHP4), non-radioactive (nr) 17β-oestradiol (nrE2) or nrP5 to identify the major gonadal steroidogenic pathways and steroid products in females and in the two male variants of this species, the terminal phase (TP) and initial phase (IP) males. Both testis and ovarian tissues exhibited 7 hydroxylase activity resulting in the formation of 7α-hydroxypregnenolone (7OHP5) from [3H]P5, and many HPLC peaks were identified as products of testicular (c. 29) and ovarian (c. 23) steroidogenesis, and only c. 50% of these metabolites co-eluted with authentic reference standards; only very small amounts of conjugated steroid were synthesized from any of the precursors. [3H]P5 was converted by testis mainly to 7αOHP5, and two unknown steroids, whereas [3H]17OHP4 metabolism gave rise to [3H]17,20β-dihydroxy-4-pregnen-3-one (DHP), 11-ketotestosterone (11KT), and two unknown steroids. For ovarian tissues, [3H]17OHP4 and [3H]P5 were metabolized to form E2, oestrone (E1), androstenedione (A4), 20α- and 20β-dihydroprogesterone (20αDHP and 20βDHP), 7αOHP5 (from [3H]P5) and a major unknown. The HPLC steroid profiles for testis incubations for IP and TP males were similar, however, the steroidogenic response of the testis of TP males to human chorionic gonadotrophin, in vitro (determined by hormone assay), was significantly higher than that of IP males.
Document Type: Regular Paper
Affiliations: 1: Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada N1G 2W1, 2: Tropical Biosphere Research Center, University of the Ryukyus, Sesoko Station, Sesoko 3422, Motobu, Okinawa 905-0227, Japan and
Publication date: June 1, 2003