title: Use of a radioimmunoassay which detects C21 steroids with a 17, 20beta-dihydroxyl configuration to identify and measure steroids involved in final oocyte maturation in female plaice (Pleuronectes platessa).
abstract: A radioimmunoassay (RIA) has been developed to detect a range of C21 (pregnane) steroids with a 17,20beta-dihydroxyl (17,20beta) configuration. In conjunction with reverse-phase high-performance liquid chromatography (HPLC), it identifies and quantifies the metabolites of 17,20beta-dihydroxy-4-pregnen-3-one, the putative "maturation-inducing steroid" in female plaice Pleuronectes platessa. Total levels of 17,20beta metabolites which can be extracted from plasma or urine with diethyl ether (i.e., free steroids) are very low (<3 ng/ml). However, total levels of 17,20beta metabolites which can be released by solvolysis (i.e., sulphated steroids) are very high (up to 1 microg/ml in plasma and 10 microg/ml in urine). On HPLC, these sulphated metabolites have been identified (in order of abundance in plasma) as: 5beta-pregnane-3alpha,17,20beta-triol, 5beta-pregnane-3beta,17,20beta-triol, 17, 20beta-dihydroxy-4-pregnen-3-one, and 17, 20beta-dihydroxy-5beta-pregnan-3-one. These steroids are absent from plasmas of fish which have not yet begun final oocyte maturation. The results support the hypothesis that 17, 20beta-dihydroxy-4-pregnen-3-one is the maturation-inducing steroid in plaice but that it is rapidly metabolised to render it inactive. The results also show that the '17,20beta'-RIA, in combination with an overnight acid solvolysis procedure, is a useful procedure for monitoring the effects of exogenous factors (such as gonadotrophin injections) on final oocyte maturation in female plaice.
authors.affiliation: Ministry of Agriculture, Fisheries and Food, Directorate of Fisheries Research, Fisheries Laboratory, Lowestoft, Suffolk, NR33 OHT, United Kingdom.
authors.forename: A P
authors.initials: AP
authors.lastname: Scott
authors.forename: R M
authors.initials: RM
authors.lastname: Inbaraj
authors.forename: E L
authors.initials: EL
authors.lastname: Vermeirssen
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D003429:Cross Reactions / Q000276:immunology; D005260:Female; D005432:Flounder; D007106:Immune Sera / Q000276:immunology; D016200:Maturation-Promoting Factor / Q000032:analysis* / Q000276:immunology; D009865:Oocytes / Q000145:classification / Q000187:drug effects / Q000254:growth & development* / Q000276:immunology; D011244:Pregnadienediols / Q000032:analysis* / Q000276:immunology; D011279:Pregnanetriol / Q000032:analysis* / Q000276:immunology; D011863:Radioimmunoassay / Q000379:methods; D013997:Time Factors; D014316:Tritium
chemical_list: D006063:Chorionic Gonadotropin; D007106:Immune Sera; D011244:Pregnadienediols; D014316:Tritium; D011279:Pregnanetriol; D016200:Maturation-Promoting Factor