Changes in potassium content and membrane potassium channels in circulating cells from normal volunteers treated with cromakalim.

The effect of cromakalim, a K+-channel activator, on the intracellular concentration and transmembrane fluxes of Na+ and K+, was studied in 18 normal male subjects, using a double-blind parallel study design. After a run-in period on placebo for 1 week the subjects were treated with either placebo (n = 6) or cromakalim (n = 12) for 1 week. Blood pressure was not changed during cromakalim administration in these normal male subjects but heart rate was increased. The intraerythrocyte and intraleucocyte K+ concentration was decreased during cromakalim administration while the Ca2+-dependent K+ channels in the red blood cells were increased. No significant effect of cromakalim could be demonstrated on the intracellular Na+ and Mg2+ concentration, on the ouabain-sensitive or bumetanide-sensitive 86Rb uptake and on the maximal 3H-ouabain binding in erythrocytes and leucocytes. The red cell Na+Li+ countertransport, anion carrier and ground membrane leak of Na+ and K+ were also not changed in the cromakalim-treated subjects.