EXTRACELLULAR ATP ACTIVATES CA2+-DEPENDENT K+ CONDUCTANCE VIA CA2+ INFLUX IN MOUSE MACROPHAGES

1. 1. Using the perforated patch recording, the effects of ATP on membrane current were investigated in mouse peritoneal macrophages. 2. 2. Extracellularly applied ATP induced a biphasic current consisting of a initial in ward current [Ii(ATP)] followed by an outward current [Io(ATP)]. These currents were associated with a marked increase in conductance at their peaks. 3. 3. Ii(ATP) reversed close to OmV and was attenuated by removal of external Na+. 4. 4. Io(ATP) reversed near - 80 mV and was increased by decreasing the external concentration of K+. 5. 5. Io(ATP) was completely abolished by removal of external Ca2+, treatment with an intracellular Ca2+ chelator, the acetoxymethyl ester of 1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetra acetic acid (BAPTA-AM) and bath applied quinidine but not tetraethylammonium (TEA) or apamin. 6. 6. These results suggest that Ii(ATP) and Io(ATP) are due to an activation of nonspecific cationic and Ca2+-dependent K+ conductances, respectively, and raise the possibility that the putative ATP receptor may be important in regulating macrophage functions, motility, phagocytosis and cytokines secretion. © 1990.