Corticosteroid metabolism in rat kidney in vitro. IV. Subcellular, sites of 11 beta-hydroxysteroid dehydrogenase activity.

An attempt has been made to identify the subcellular localization of renal corticosteroid metabolism. Subcellular fractions were prepared by differential centrifugation, identified by marker enzymes and incubated under different conditions with corticosterone (B). The NADP+/NADPH dependent metabolism of B could be localized in the nuclear and microsomal fraction. The most prominent metabolite was 11-dehydro-B, which is formed by 11 beta-hydroxysteroid dehydrogenase (EC 1.1.1.146). Enzyme kinetic studies of this enzyme with B as substrate revealed apparent Km-values in the range of 10(-7) M for both the nuclear and microsomal fraction.