Activation of the rat kidney mineralocorticoid receptor

Activation of the rat kidney mineralocorticoid receptor was investigated using DEAE-cellulose, DNA-cellulose and gel permeation chromatography. Specific labeling of the mineralocorticoid receptor was achieved by labeling with [3H]aldosterone in the presence of the pure glucocorticoid RU28362. The specificity of labeling was confirmed by the lack of immunoreactivity of [3H]aldosterone-labeled material with the monoclonal antiglucocorticoid receptor antibody BUGR-1. The unactivated aldosterone-mineralocorticoid receptor complex did not bind to DNA-cellulose, was eluted from DEAE-cellulose at relatively high salt (190 mM KCl) concentration and had an apparent Stokes radius when chromatographed on Sephacryl S300 of 6.3 nm. After activation (at 250C for 20 min), the aldosterone-mineralocorticoid receptor complex had increased affinity for DNA-cellulose, decreased affinity for DEAE-cellulose and appeared as a smaller complex when chromatographed on Sephacryl S300. These changes were blocked by sodium molybdate. The authors results indicate that activation of the rat kidney mineralocorticoid receptor is analogous to activation of the glucocorticoid receptor and suggest that activation of the mineralocorticoid receptor involves dissociation of a multimeric receptor form