Interaction of rat liver glucocorticoid receptor with heparin

When rat liver cytosol containing [³H]dexamethasone-glucocorticoid receptor complex is exposed to immobilized heparin (Sepharose-heparin; Seph-hep) the steroid receptor complex binds to the substituted Sepharose avidly [K_d = 3.5 (±1.7) × 10^-10 M], and 80-90% of the receptor present is adsorbed to the solid phase after 40 min at 0°C. The binding is enhanced by Mn²⁺ (10 mM) and Mg²⁺, whereas Ca²⁺ and Sr²⁺ are ineffective. Sodium molybdate (10 mM) does not influence the reaction but enhances receptor stability. Moreover, binding of the receptor to Seph-hep is dependent on the ionic strength of the medium, because binding is totally reversed by 300 mM KCl. The bound [³H]dexamethasone-receptor complex can be recovered from Seph-hep with solutions (4 mg/mL) of heparin (95% release), dextran sulfate (88%), and chondroitin sulfate (63%); total calf liver RNA is less effective (9%), whereas dextran, D-glucosamine, N-acetyl-D-glucosamine, D-glucuronic acid, and sheared calf thymus DNA are totally ineffective (3H] dexamethasone-receptor bound to the resin.