NONCLASSICAL RECEPTORS FOR ALDOSTERONE IN PLASMA-MEMBRANES FROM PIG KIDNEYS

Rapid, nongenomic in vitro effects of aldosterone on intracellular electrolytes, cell volume and the sodium-proton antiporter have been found in human mononuclear leukocytes (HML), as have related membrane receptors. In the present study, binding of I-125-labeled aldosterone to plasma membrane preparations from pig kidneys was studied, since nongenomic in vitro effects of aldosterone have also been described in cultured kidney cells. In this preparation, binding of aldosterone shares important features with both functional and binding data in HML. These include a very low apparent K-i of similar to 0.1 nM for aldosterone, a high turnover rate and binding selectivity for aldosterone and fludrocortisone. Desoxycorticosterone acetate and corticosterone show intermediate affinity, with apparent K-i values of similar to 1 and 100 nM, with hydrocortisone even less active. Thus binding of aldosterone to kidney plasma membranes is compatible with the major features of its nongenomic renal effects.