Mineralocorticoid receptors in the rat lung

In lung cytosol from adrenalectomized rats, tritiated aldosterone binds to two classes of limited capacity sites with affinities (Kd at 37 C) of 0.7 and 80 nM. The predominant binding species sediments at approximately 9S on sucrose density gradients in low ionic strength, molybdate-containing buffer. Binding of tritiated aldosterone (5 nM) is displaced by a 4-fold excess of nonradioactive hormone in the following hierarchy: 9 alpha-fluorocortisol greater than aldosterone greater than deoxycorticosterone much greater than corticosterone greater than dexamethasone. Thus, pulmonary tissue contains steroid-binding sites with affinity and specificity characteristics equivalent to those previously shown for mineralocorticoid receptors in classic target tissues. The pulmonary cell type(s) in which these putative mineralocorticoid receptors are located and possible physiological roles for mineralocorticoids in adult and fetal lung remain to be explored.