Adrenocorticotropic hormone activates an outward current in cultured mouse peritoneal macrophages

To define the effects of adrenocorticotropic hormone (ACTH) in immunocompetent cells, ion channel activities in cultured mouse peritoneal macrophages were analyzed by the perforated patch-clamp method. ACTH induced outward currents at smaller holding potentials than K+ equilibrium potentials. Reversal potentials of ACTH-induced currents were dependent on external K+ concentrations, but not on external Cl- concentration. Quinine potently blocked the outward current and tetraethylammonium (TEA) partially suppressed that current. ACTH did not induce the response in Ca2+ free solution containing EGTA. These results suggest that ACTH can modulate macrophage functions through the activation of Ca2+ dependent K+ channels.