K channels of human alveolar macrophages.

The activation of macrophages has been reported to be associated with Ca-activated K permeability change. In order to study this permeability change in human alveolar macrophages, we examined alveolar macrophages electrophysiologically at a single channel level. We observed two types of Ca-activated K channel currents having conductances of 218 +/- 2 and 32 +/- 0.6 picosiemens in symmetrical 154 mmol/L KCl solutions. The characteristics, such as voltage dependency and Ca sensitivity, as well as channel conductance, were different between these two types of channel currents. Quinine (a blocker of Ca-activated K conductance), 0.5 mmol/L, reduced these channel currents by 45 +/- 8% and 31 +/- 8%. Quinine, 0.5 mmol/L, also inhibited chemiluminescence and leukotriene B4 release by 82 +/- 6 to 88 +/- 3% and 88 +/- 2%, respectively. These results suggest the presence of two types of Ca-activated K channels, which may be related to the release of inflammatory mediators from human alveolar macrophages.