Steroid binding to cardiac type I receptors: in vivo studies

In vitro, Type I (mineralocorticoid) receptors show equivalently high affinity for aldosterone, corticosterone and cortisol in cytosol preparations from a wide range of tissues. This steroid non-selectivity is also found for hippocampal Type I receptors in vivo; in contrast, Type I receptors in physiological mineralcorticoid target tissues are highly aldosterone-specific in vivo. In the present study we show that Type I receptors in the heart are non-selective in vivo, like those in hippocampus, and therefore presumably act as high-affinity glucocorticoid receptors rather than mineralocorticoid receptors.