Glucocorticoid receptor binding was compared in liver cytosol preparations from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats using homologous displacement of [3H]dexamethasone. At 5 degrees C, there was no difference in receptor binding affinity or concentration between strains for dexamethasone, corticosterone or aldosterone. At 37 degrees C, affinity for dexamethasone was lower than at 5 degrees C for both rat strains and decreased with time. However, at this higher temperature, binding affinity in the SHR preparation was consistently higher than in the WKY preparation. The WKY preparation had a higher receptor concentration. The rate of dissociation of the [3H]dexamethasone-receptor complex prepared at 5 degrees C and then incubated at 37 degrees C was rapid but not different between strains. A possible explanation of these results is that the relationship of the heat shock proteins to the receptor heterocomplex is different between strains. Evidence exists of a genetic difference in Hsp 70 between SHR and WKY rats, although its cosegregation with blood pressure has not been established.