RT Journal Article
SR Electronic
T1 CHARACTERIZATION OF TESTOSTERONE 11β-HYDROXYLATION CATALYZED BY HUMAN LIVER MICROSOMAL CYTOCHROMES P450
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 714
OP 718
DO 10.1124/dmd.104.003327
VO 33
IS 6
A1 Man Ho Choi
A1 Paul L. Skipper
A1 John S. Wishnok
A1 Steven R. Tannenbaum
YR 2005
UL http://dmd.aspetjournals.org/content/33/6/714.abstract
AB A combination of accelerator mass spectrometry (AMS) and liquid chromatography-tandem mass spectrometry has been used to clarify some new aspects of testosterone metabolism. The main pathway of testosterone oxidative metabolism by human liver microsomes is the formation of 1β-, 2α-/β-, 6β-, 15β-, and 16β-hydroxytestosterones, mainly catalyzed by cytochromes P450 2C9, 2C19, and 3A4. We now report the first determination that 11β-hydroxytestosterone (11β-OHT) can also be formed by human liver microsomal fractions. The structures of five hydroxylated metabolites of testosterone (2β-, 6β-, 11β-, 15β-, and 16β-OHT) and the C-17 oxidative metabolite androstenedione were determined by liquid chromatography with UV detection at 240 nm and liquid chromatography-tandem mass spectrometry. Corresponding results were obtained by high-performance liquid chromatography-AMS analysis of incubations of [4-14C]testosterone with human liver microsomes. 6β-Hydroxylation was always the dominant metabolic pathway, but 2β-, 15β-, and 16β-OHT, and androstenedione were also formed. The previously undetected hydroxytestosterone, 11β-OHT, was found to be a minor metabolite formed by human liver microsomal enzymes. It was formed more readily by CYP3A4 than by either CYP2C9 or CYP2C19. 11β-Hydroxylation was inhibited by ketoconazole (IC50 = 30 nM) at concentrations similar to the IC50 (36 nM) for 6β-hydroxylation Therefore, CYP3A4 could be mainly responsible for testosterone 11β-hydroxylation in the human liver. These findings identify human hepatic biotransformation of testosterone to 11β-OHT as a previously unrecognized extra-adrenal metabolic pathway. The American Society for Pharmacology and Experimental Therapeutics