Activation of single Ca2+‐dependent K+ channel by external ATP in mouse macrophages

Abstract

Single Ca²⁺‐dependent K⁺ currents responding to external ATP were recorded from cell‐attached patches on mouse peritoneal macrophages. Extracellularly applied ATP activated an inward single‐channel current with a conductance of 25 pS and a reversal potential of −79 mV (pipette potential, V _p) when the pipette contained a 145 mM KC1 solution. The reversal potential was shifted 56 mV positive by a 10‐fold reduction in external (pipette) K⁺ concentration. The effect of ATP was abolished by either removal of external Ca²⁺ or treatment with an intracellular Ca²⁺ chelator, the acetoxymethyl ester of 1,2‐bis (2‐aminophenoxy)ethane‐N,N,N',N'‐tetraacetic acid (BAPTA‐AM). This channel has a mean open time of 9.1 ms and open probability was not strongly dependent on V _p in the range tested (+ 120 to −30 mV).