Vascular type I aldosterone binding sites are physiological mineralocorticoid receptors.

In vitro, Type I receptors have high and equivalent affinity for aldosterone, corticosterone and cortisol: in vivo, physiological mineralocorticoid target tissues (kidney, colon, parotid) are highly aldosterone-selective, in contrast with hippocampus and heart. In the present study we show that the mesenteric vascular arcade is similarly highly aldosterone-selective in vivo, and in vitro shows considerable levels of 11 beta OH steroid dehydrogenase activity, previously postulated as the mechanism whereby glucocorticoids are excluded from physiological mineralocorticoid receptors.