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Aldosterone binding sites in human mononuclear leukocytes were characterized after separation of cells from blood by a Percoll gradient. After washing and resuspension in RPMI-1640 medium, cells were incubated at 37 degrees C for 1 h with different concentrations of [3H]aldosterone plus a 100-fold concentration of RU-26988 (11 alpha, 17 alpha-dihydroxy-17 beta-propynylandrost-1,4,6-trien-3-one), with or without an excess of unlabeled aldosterone. Aldosterone binds to a single class of receptors with an affinity of 2.7 +/- 0.5 nM (means +/- SD, n = 14) and a capacity of 290 +/- 108 sites/cell (n = 14). The specificity data show a hierarchy of affinity of desoxycorticosterone = corticosterone = aldosterone greater than hydrocortisone greater than dexamethasone. The results indicate that mononuclear leukocytes could be useful for studying the physiological significance of these mineralocorticoid receptors and their regulation in humans.

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