Mineralocorticoid Receptors in Human Kidney

Cytosol binding of 3Haldosterone was measured after incubation of the hormone at 37 C with slices of human kidney obtained after surgical removal. High affinity 3Haldosterone binding with an apparent equilibrium dissociation constant (Kd) of approximately 0.5 nM was observed to probably "mineralo-corticoid receptors." 3Haldosterone binding of lower affinity and higher capacity (probably to "glucocorticoid receptors") was also observed. Binding of other steroids by the mineralocorticoid receptors was determined by competitive analysis using a low concentration of 3Haldosterone (so that 3H binding is predominantly by the mineralocorticoid receptors). The binding activities relative to aldosterone (100%) were: deoxycorticosterone, 48%; cortisol, 1.5%; 18-hydroxy-deoxycorticosterone, 1.2%; and 18-hydroxy-corticosterone, 0.2%. The relative sodium-retaining potencies of these steroids in vivo correlate well with their binding activities. These data provide further support to the view that the major high affinity 3Haldosterone binding is by mineralocorticoid receptors. Two steroids, 16beta-hydroxy-dehydroepiandrosterone and 16-oxo-androstenediol, recently shown to have sodium-retaining activity in the rat, and also implicated in low-renin "essential" hypertension in man, showed no competitive binding activity. The affinity of 3Haldosterone for binding to these mineralocorticoid receptors and the relative steroid binding activities are similar to the values previously reported in the rat. Thus, human and rat mineralocorticoid receptors appear to be similar in their affinity for aldosterone and their specificity for binding a number of other steroids.