CHARACTERIZATION OF TESTOSTERONE 11-HYDROXYLATION CATALYZED BY HUMAN LIVER MICROSOMAL CYTOCHROMES

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 mi-crosomes is the formation of 1-, 2-/-, 6-, 15-, and 16-hydroxytestosterones, mainly catalyzed by cytochromes P450 2C9, 2C19, and 3A4. We now report the first determination that 11-hydroxytestosterone (11-OHT) can also be formed by human liver microsomal fractions. The structures of five hydroxylated metab-olites of testosterone (2-, 6-, 11-, 15-, and 16-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 re-sults were obtained by high-performance liquid chromatography-AMS analysis of incubations of [4-14C]testosterone with huma