Sex differences in the distribution and regulation of glucocorticoid receptors in cardiac tissues of rats.

We compared the binding of [3H]-dexamethasone in cytosols prepared from atria and ventricles. The effects of steroid treatment and adrenalectomy on receptor concentration were measured in both male and female rats. In male rats the distribution of receptors was similar in atria and ventricles. In contrast, the atria of female rats in all treatment groups had twice the number of receptors as did the ventricles. Adrenalectomy in females resulted in receptor up-regulation, but dexamethasone treatment, which was effective in reducing binding in males and in the ventricles of females, failed to alter atrial binding in females. These results suggest that the atria of female rats may be more responsive than ventricles to the effects of circulating glucocorticoids.