Metabolism of anabolic steroids by recombinant human cytochrome P450 enzymes: Gas chromatographic-mass spectrometric determination of metabolites

Metabolism of steroid hormones with anabolic properties was studied in vitr o using human recombinant CYP3A4, CYP2C9 and 2B6 enzymes. The enzyme format s used for CYP3A4 and CYP2C9 were insect cell microsomes expressing human C YP enzymes and purified recombinant human CYP enzymes in a reconstituted sy stem. CYP3A4 enzyme formals incubated with anabolic steroids, testosterone, 17 alpha-methyltestosterone, metandienone, boldenone and 4-chloro-1,2-dehy dro-17 alpha-methyltestosterone, produced 6 beta-hydroxyl metabolites ident ified as trimethylsilyl (TMS)-ethers by a gas chromatography-mass spectrome try (GC-MS) method. When the same formats of CYP2C9 were incubated with the anabolic steroids, no 6 beta-hydroxyl metabolites were formed. Human lymph oblast cell microsomes expressing human CYP2B6 incubated with the steroids investigated produced traces of 6 beta-hydroxyl metabolites with testostero ne and 17 alpha-methyltestosterone only. We suggest that the electronic eff ects of the 3-keto-4-ene structural moiety contribute to the selectivity wi thin the active site of CYP3A4 enzyme resulting in selective 6 beta-hydroxy lation. (C) 1999 Elsevier Science B.V. All rights reserved.