Extracellular ATP activates Ca2(+)-dependent K+ conductance via Ca2+ influx in mouse macrophages.
1. Using the perforated patch recording, the effects of ATP on membrane current were investigated in mouse peritoneal macrophages. 2. Extracellularly applied ATP induced a biphasic current consisting of a initial inward current [Ii(ATP)] followed by an outward current [Io(ATP)]. These currents were associated with a marked increase in conductance at their peaks. 3. Ii(ATP) reversed close to 0 mV and was attenuated by removal of external Na+. 4. Io(ATP) reversed near -80 mV and was increased by decreasing the external concentration of K+. 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. 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.
Hara
N
N
Central Research Laboratories, Shimane Medical University, Izumo, Japan.
Ichinose
M
M
Sawada
M
M
Maeno
T
T
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004553:Electric Conductivity; D008264:Macrophages / Q000378:metabolism* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology
D015221:Potassium Channels; D000255:Adenosine Triphosphate; D011188:Potassium; D002118:Calcium