REDUCTION OF 3-OXOSTEROIDS IN HUMAN LIVER MICROSOMES

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Abstract
The 3α- and 3β-reduction of the following steroids was studied in human liver microsomes: 5α-androstane-3,17-dione, 17β-hydroxy-5α-androstan-3-one, 5α-pregnane-3,20-dione, 5β-pregnane-3,20-dione, 3-oxo-5β-cholanoic acid and 7α-hydroxy-5α-cholestan-3-one. With NADH as cofactor there was a preferential 3α-reduction of the C19- and C21-3-oxo-steroids and a preferential 3β-reduction of the C24- and C27-3-oxo-steroids. Substitution of NADH with NADPH influenced reduction of the substrates in different ways, indicating the presence of several 3α- and 3β-hydroxysteroid dehydrogenases with different substrate specificity and specificity towards NADH and NADPH. Only small or insignificant sex differences could be observed in the reductions studied.