LOCALIZATION OF THE GLUCOCORTICOID RECEPTOR IN RAT-LIVER CELLS - EVIDENCE FOR PLASMA-MEMBRANE BOUND RECEPTOR

1. The cytoplasmic glucocorticoid receptor of rat liver cells is in pa rt recovered in the plasma membrane fraction. 2. After in vivo adminis tration of [H-3]dexamethasone, 0.35% of the radioactivity recovered is bound on plasma membranes. 3. Dexamethasone also binds in vitro speci fically to plasma membranes. Expressed as fmol/mg protein, binding of dexamethasone to plasma membranes is comparable to binding to the solu ble cytoplasmic fraction (cytosol). 4. Using polyclonal antibody to th e glucocorticoid receptor and the indirect immunofluorescence technic, an intense decoration of the plasma membranes is observed, denoting a high concentration of glucocorticoid receptor on plasma membranes. 5. The localization of the receptor on plasma membranes could be of pote ntial importance for its interaction with agents (mitogens, growth fac tors) initially acting on the cell membrane, regulating subsequent cel l proliferation and growth at the level of the cell nucleus.