[Evidence for the presence of glucocorticoid receptors in heart contractile cells].

Using 3H-labelled glucocorticoids, the receptor activity of heart and liver cytosol preparations from various animal classes and species, the distribution of receptors in the myocardium from different divisions of rat heart and the number of glucocorticoid receptors in the myocyte preparations isolated from adult rat hearts after treatment of cardiac tissue with hyaluronidase and collagenase have been studied. The specific binding of 3H-dexametasone to bovine fetal heart endothelial cells as well as to some other cell cultures was investigated. The data obtained suggest that the bulk of the total receptor activity of the heart is accounted for contractile cells of the myocardium. The number of specific sites of glucocorticoid binding by whole myocyte cells (per 1 mg of protein) or by "crude nuclear fraction" (per 1 mg of DNA) is comparable to that for some other cell types, which are believed to be hormone-sensitive. However, by the number of receptors per single cell myocytes surpass all the other cell types under study.