title: Aromatization of [4-14C]testosterone to [14C]estradiol-17 beta by testicular tissue from male-to-female transsexuals on estrogen therapy.
abstract: Abnormality in testicular biosynthesis of sex hormones may accompany or cause transsexualism. With a view to determine whether the cells of male transsexual testicular tissue possess aromatic cytochrome P-450 activity, homogenates of the tissue from 4 phenotypic male-to-female transsexuals (2 Chinese and 2 Malays, aged 23-34 years) with XY karyotype who had been on estrogen therapy for 9-17 years until orchidectomy were incubated with [4-14C]testosterone as substrate. Using reverse-isotope dilution analysis, identity was established for [14C]estradiol-17 beta. No such metabolite was found in parallel incubations of heat-denatured enzymes. The extent of enzyme-catalyzed conversion was 9.3 x 10(-3) to 3.4 x 10(-2)%. The specific biosynthetic aromatase cytochrome P-450 activity contained in the tissue system can synthesize [14C]estradiol-17 beta from [4-14C]testosterone. Elevated aromatic expression in situ may have important effects on target tissues.
authors.affiliation: Institute of Science and Forensic Medicine, National Blood Centre, Singapore, Republic of Singapore.
authors.forename: R
authors.initials: R
authors.lastname: Gunasegaram
authors.forename: A
authors.initials: A
authors.lastname: Loganath
authors.forename: K L
authors.initials: KL
authors.lastname: Peh
authors.forename: S S
authors.initials: SS
authors.lastname: Ratnam
mesh_terms: D000328:Adult; D001141:Aromatase / Q000378:metabolism* / Q000502:physiology; D002250:Carbon Radioisotopes; D002855:Chromatography, Thin Layer; D004958:Estradiol / Q000378:metabolism* / Q000502:physiology; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D010641:Phenotype; D013737:Testis / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D013739:Testosterone / Q000378:metabolism* / Q000502:physiology; D014189:Transsexualism / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D004967:Estrogens; D013739:Testosterone; D004958:Estradiol; D001141:Aromatase