An antiserum to the rat liver glucocorticoid receptor

A rabbit immunized with a highly purified preparation of rat liver [3H]triamcinolone-receptor complex developed antibodies to the receptor. Although precipitating reactions were not detected, complexes formed between IgG and the receptor could be detected by Staphylococcus aureus protein A-Sepharose and gel permeation chromatography. IgG was purified and covalently immobilized on Sepharose CL-4B; this affinity matrix adsorbed the ligand-free receptor and both activated and nonactivated forms of the [3H]triamcinolone-receptor complex. Rat liver cytosol proteins adsorbed by control and immune immunoglobulin-Sepharoses were eluted with 0.1 M acetic acid and analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. A protein with molecular weight 78,000 was the major species eluted from immune immunglobulin-Sepharose, and it was not present in eluates from control columns. Rat transcortin, glucocorticoid binder IB, and an estrogen-binding protein from rat liver were not adsorbed by immune IgG-Sepharose. Mouse and hamster liver glucocorticoid receptors showed only limited adsorption. Thus, the antiserum does not crossreact with other major glucocorticoid-binding proteins and demonstrates species specificity.