Corticosteroid metabolism in rat kidney in vitro

Abstract
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 11β-hydroxysteroid dehydrogenase (EC 1.1.1.146). Enzyme kinetic studies of this enzyme with B as substrate revealed apparentK m-values in the range of 10−7 M for both the nuclear and microsomal fraction.