Metabolism of 2-hydroxy-3-deoxyestradiol by rat liver microsomes

Abstract

The biotransformation of [6,7- 3H]2-hydroxy-3-deoxyestradiol, which is a positional isomer of the naturally occurring estrogen, has been investigated with rat liver microsomes. 2-Hydroxyestradiol separated from the lipophilic fraction of the incubation mixture was unequivocally characterized by means of thin-layer chromatography, gas chromatography-mass spectrometry, and the reverse isotope dilution method. The formation of glutathione 1- and 4-thioethers of 2-hydroxyestradiol as watersoluble metabolites was also confirmed by chromatographic properties and coloration tests, followed by reverse isotope dilution analysis of the aglycone produced by desulfurization with Raney nickel. Incubation of [3- 2H]2-hydroxy-3-deoxyestradiol with rat liver microsomes yielded 2-hydroxyestradiol without any retention of the label, indicating that C-3 hydroxylation proceeded through a quinoid intermediate. When a 1 to 1 mixture of 3-deuterated and nonlabeled 2-hydroxy-3-deoxyestradiols was incubated, no substantial change was seen in the deuterium content with the recovered substrate, which implied the absence of the isotope effect in C-3 hydroxylation.