Biosynthesis of 6β-hydroxytestosterone from testosterone by human fetal liver microsomes

6β-Hydroxytestosterone has been isolated and characterized after incubation of 4-[¹⁴C]-testosterone with 105,000 × g-microsomes of human fetal liver. The presence of 6β-hydroxylase activity in the fetal liver microsomes indicates that the fetal liver - as well as the placenta - is able to form 6β-hydroxy-C₁₉-steroids. The 6β-hydroxytestosterone formed in the fetal liver can be considered as a precursor of the 6-hydroxylated estrogens found in human pregnancy urine. The isolation of this metabolite was carried out by thin-layer chromatographic techniques; the identity of the 6β-hydroxy-testosterone was established by its behaviour on thin-layer chromatography and on gas-liquid chromatography as well as by gas chromatography-mass spectrometry.