title: Inhibition of rat testicular microsomal steroidogenesis by oxytocin and metyrapone.
abstract: Capillary gas chromatographic 'steroid profiling' has been utilised to separate and quantify the metabolites (derivatized as methyloximes and/or trimethylsilyl ethers) formed from pregnenolone after incubation with rat testicular microsomes. A wide range of steroid metabolites was found, indicating that both the 5-ene and 4-ene pathways of testosterone biosynthesis were operating, as well as 16 alpha-hydroxylation, 20 beta-reduction and the formation of several C19 steroids (the 16-androstenes). At the concentration used, Metyrapone markedly inhibited 16 alpha- and 17-hydroxylation and side-chain cleavage of 17-hydroxylated C21 steroids. 16-Androstene production was also markedly inhibited and the formation of other metabolites was affected to lesser extents. Oxytocin abolished the formation of all C21 and C19 metabolites of pregnenolone.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: T K
authors.initials: TK
authors.lastname: Kwan
authors.forename: D B
authors.initials: DB
authors.lastname: Gower
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D002849:Chromatography, Gas; D000072467:Cytochrome P450 Family 2; D066298:In Vitro Techniques; D008297:Male; D008797:Metyrapone / Q000494:pharmacology*; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D010121:Oxytocin / Q000494:pharmacology*; D011284:Pregnenolone / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D039181:Steroid 16-alpha-Hydroxylase; D013256:Steroids / Q000096:biosynthesis*; D013737:Testis / Q000187:drug effects* / Q000378:metabolism
chemical_list: D013256:Steroids; D010121:Oxytocin; D011284:Pregnenolone; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; D008797:Metyrapone