Neurosteroids: Metabolism in human intestine microsomes

To achieve this, we produced radio-labeled 7α-hydroxy-DHEA, 7β-hydroxy-DHEA, 7α-hydroxy-EpiA and 7β-hydroxy-EpiA that were used as substrates in incubations with human intestine microsomes supplemented with reduced or oxidized cofactors. Identity of the radio-labeled metabolites obtained was determined by gas chromatography/mass spectrometry after comparison with authentic steroid references. The proportions of metabolites produced resulted from their radioactivity contents. The only metabolite obtained with DHEA, EpiA, 7α-hydroxy-DHEA and 7β-hydroxy-DHEA substrates was its 17β-reduced derivative, thus inferring the presence of 17β-hydroxysteroid oxidoreductases in the human intestine microsomes. In addition to the 7α-hydroxy-EpiA and 7β-hydroxy-EpiA substrates, their 17β-reduced metabolites were obtained with 7β-hydroxy-EpiA and 7α-hydroxy-EpiA, respectively. The identity of the enzyme responsible for the 7α-hydroxy-EpiA/7β-hydroxy-EpiA inter-conversion is unknown. The incubation conditions used produced these metabolites in low but significant yields that suggest their presence in the portal blood before access to the liver.