Characteristics of glucocorticoid binding to mouse liver cytosol

Abstract

Mouse liver cytosol contains a protein which binds the synthetic glucocorticoid, triamcinolone acetonide. Binding was analyzed by the charcoal assay and sucrose density gradient techniques. Sucrose density gradient analysis under low ionic strength conditions revealed a 7.4 S peak of binding activity. This binding was altered to 4 S under high ionic strength conditions. Mouse serum did not bind triamcinolone acetonide. Cytosol binding was of high affinity ( K D = 3.7 × 10 −9M) and the concentrations of sites was 3 × 10 −13 mol/mg protein. Competitive binding analysis revealed a glucocorticoid preference which was very similar to that of the AtT-20 mouse pituitary tumor cell line glucocorticoid receptor. The degradation of cytosol binding at 37°C was slowed by the presence of sodium molybdate. This effect was not due to a measurable change in the dissociation rate of the receptor or to the sodium component of the molybdate. These studies show that mouse liver cytosol contains a glucocorticoid receptor with properties very similar to those of the AtT-20 cell glucocorticoid receptor.