Identical Properties of Aldosterone and Corticosterone Binders and Their Presence in Rat Brain and Kidney

Publisher Website
Google Scholar
Abstract
The [3H] corticosterone binders from rat brmn and kidney were characterized by binding affinity and chromatographies, and compared with the binders for [3H]aldosterone and [3H] triamcinolone acetonide.Corticosterone-binding globulin-like molecules at very high concentrations in crude extracts were completely eliminated by a DEAE-gel adsorption procedure. [3H] Aldosterone binder in the renal, DEAE-treated fraction was recovered in a single peak by gel-filtration chromatography and by ultracentrifugation in linear sucrose gradients, independent of hormone-binding and tungstate, a stabilizer of the binder. The Stokes‘ radius and sedimentation coefficient of the renal aldosterone binder were 6.6 nm and 9.3S, respectively, indicating an apparent molecular weight of 263, 000. Corticosterone-preferring binder also existed in the DEAE-treated fraction. Both aldosterone and corticosterone binders were found in the brain and kidney preparations. Comparison among the binders showed identical values of Stokes’ radius and elution pattern from DEAE-Toyopearl in a linear salt gradient regardless of the organ and the hormones. Scatchard analyses of [3H]aldosterone and [3H]corticosterone binding showed for each ligand only one group of high-affinity sites with the equivalent dissociation constants, 4–7 nM. The orders of steroids in competing for the two high-affinity sites were equivalent: corticosterone ≥aldosterone ≫triamcinolone acetonide, and that for the triamcinolone acetonide binding was triamcinolone acetonide≫aldosterone≥corticosterone. Hydroxyapatite column chromatography separated the aldosterone and corticosterone binders from the triamcinolone acetonide binder, but not the aldosterone binder from the corticosterone binder. It is concluded that aldosterone and corticosterone binders distinct from triamcinolone acetonide binder exist in rat brain and kidney. The corticosterone binder is very similar or identical to the aldosterone binder.