Corticosterone binding in myocardial tissue of rats after chronic stress and adrenalectomy.

Male rats were trained to swim for 9-10 days to assess the effect of chronic stress on the capacity and affinity of specific glucocorticoid binding in the cytosol fraction of myocardial tissue. A significant decrease in the binding capacity for corticosterone (Cpd B) was found 24 hours after the last swimming test, while the affinity constant remained unchanged. Contrary to Cpd B binding, there was no change in the capacity of dexamethasone binding, and there was no decrease in the Cpd B binding capacity in rats which had been adrenalectomized 2 days prior to the training period. We conclude that daily swimming for 9-10 days alters the numbers of cytoplasmic Cpd B binding sites in the face of increased adrenocortical activity, while not affecting dexamethasone binding in the cytosol fraction of myocardial tissue.