Interconversion between 17β‐Hydroxy‐5α‐androstan‐3‐one (5α‐Dihydrotestosterone) and 5α‐Androstane‐3α,17 β‐diol in Rat Kidney: Heterogeneity of 3α‐Hydroxysteroid Oxidoreductases

Publisher Website
Google Scholar
Abstract
3.alpha.-Hydroxysteroid oxidoreductases [EC 1.1.1.50] catalyzing the interconversion between 17.beta.-hydroxy-5.alpha.-androstan-3-one (5.alpha.-dihydrotestosterone) and 5.alpha.-androstane-3.alpha.,17.beta.-diol (3.alpha.-androstanediol) were studied in rat kidney. Three enzymes can be distinguished: a soluble NADPH-dependent oxidoreductase, a microsomal NADPH-dependent enzyme and a microsomal NADH-linked enzyme. Traces of the microsomal enzymes are consistently observed in the 108,000 x g supernatant. Studies on crude preparations reveal that these enzymes differ not only in subcellular localization and cofactor requirement, but also in optimum pH, kinetic characteristics, sensitivity to potential steroidal inhibitors and sensitivity to detergents, ionic strength and temperature. Salient sex differences exist in the activity of all 3 kidney enzymes. The soluble NADPH-dependent enzyme is more active in female rats whereas both microsomal enzymes are considerably more active in male animals. The microsomal NADH-dependent oxidoreductase displays favorable characteristics to catalyze the 3.alpha.-dehydrogenation of 3.alpha.-androstanediol. It is mainly this enzyme that enables the kidney to use 3.alpha.-androstanediol as an efficient precursor for the local formation of 5.alpha.-dihydrotestosterone.

This publication has 44 references indexed in Scilit: