Characterization of Specific Binding Sites for Corticosterone in Mouse Liver Plasma Membrane

Abstract

The specific binding of [³H]corticosterone to mouse liver purified plasma membrane fractions is a saturable, reversible, and temperature-dependent process. Only one type of independent and equivalent binding sites has been determined in plasma membrane (K_d = 4.1 nM and Bmax = 3368 fmol/mg). As can be deduced from displacement data obtained in plasma membrane, the high-affinity binding site is different from nuclear glucocorticoid, nuclear progesterone, and Na⁺, K⁺-ATPase digitalis receptors. Probably this corticosterone binding site or receptor is the same one determined previously for [³H]cortisol in mouse liver plasma membrane. Such β- and α-adrenergic antagonists as propranolol and phentolamine did not affect [³H]corticosterone binding to plasma membranes; therefore, this binding site is independent of these receptors. The binding sites in plasma membranes are not exclusive for corticosterone, but other steroids are also bound with very different affinities

Key Words:

• Corticosterone
• plasma membranes
• glucocorticoids
• specific binding sites
• steroids
• mouse liver