ALDOSTERONE INFLUENCES FREE INTRACELLULAR CALCIUM IN HUMAN MONONUCLEAR LEUKOCYTES INVITRO

Mineralocorticoid receptors have been detected in human mononuclear leukocytes (HML) and a physiological effector mechanism was demonstrated subsequently by which aldosterone is able to prevent the loss of intracellular sodium, potassium and cell water during incubation in an aldosterone-free medium. In the present paper, free intracellular calcium, [Ca2+]i, was measured in HML from normal subjects by Quin-2 and Fura-2 fluorescence after incubation for 1 h at 37°C in RPMI-1640 medium. In fresh HML, [Ca2+]i was 54 ± 15 nM (Fura-2, mean ± SD, n = 26). After incubation without aldosterone, [Ca2+]i in HML was 118 ± 27 nM (Quin-2, n = 11) and 50 ± 13 nM (Fura-2). After incubation with 1.4 (Fura-2) or 2.8 nM (Quin-2) aldosterone, [Ca2+]i was 139 ± 38 nM (Quin-2, P < 0.05 compared with value after incubation without aldosterone) and 57 ± 11 nM (Fura-2, P < 0.00001). The Kd-value for dose-response curve was 0.4 nM. The effect of aldosterone was antagonized by N-ethyl-isopropylamiloride, but not by canrenoate, canrenone, cycloheximide and actinomycin D. It was absent in a sodium-free buffer. Corticosterone and hydrocortisone were active as agonists. These results show that aldosterone exerts an effect on the [Ca2+]i in HML in vitro which could be involved in hemodynamic responses to mineralocorticoids if also present in cardiovascular tissues. © 1990.