Nongenomic effect of aldosterone on ion transport pathways of red blood cells

The direct influence of aldosterone on the human and avian red blood cell (RBC) transport systems, Na+/K+ pump, Na+, K+, 2Cl(-) symporter, and K+(Na+)/H+ exchanger, was investigated with tracer kinetics. The present work proved that aldosterone has no significant effect on these transport pathways. However, in young human RBCs containing reticulocytes aldosterone showed a significant inhibition of the Na+, K+, 2Clsymporter. Investigations of the Li+ efflux via the Na+/Li+ exchanger using atom absorption spectroscopy revealed that aldosterone has no effect on this transporter. Studies of the effect of aldosterone on the Ca2+ content and the intracellular pH (pH(i)) were carried out on single RBCs with a fluorescence imaging system. Both parameters are affected by aldosterone. The Ca2+ uptake in the presence of aldosterone, under conditions where the Ca2+ pump is inhibited, showed marked differences from the control. Since the effect is nifedipine-sensitive, it seems that aldosterone affects a Ca2+ channel. In addition, aldosterone leads to an acidification of the intracellular medium after an initial alkalisation due to an effect on the Na+/H+ exchanger. Copyright (C) 2008 S. Karger AG, Basel.