Interaction of [ 3H]-aldosterone with rat kidney plasma membranes

Abstract

The interaction of [ 3H]-aldosterone with isolated rat kidney plasma membranes has been studied by centrifugation and gel filtration methods. The Scatchard plot analysis of data indicated the affinity of aldosterone for membrane sites, expressed as equilibrium constant K diss , to be 1.3 × 10 −8M and the concentration of binding sites ( n) 1.69 × 10 −13 mol/mg protein. The high concentration of unlabelled aldosterone present in the incubation medium, or injected into rats 45 min before killing, decreased the amount of labelled aldosterone bound to plasma membranes. Gel filtration on Sephadex G-200 and disc electrophoresis on polyacrylamide gel of solubilized [ 3H]-aldosterone-renal plasma membranes complex showed that the hormone was bound to the high molecular weight protein component of the plasma membranes. The proteinaceous nature of membrane component which bound aldosterone was determined using delipidated plasma membranes.