Differential Expression of Inward and Outward Potassium Currents in the Macrophage-Like Cell Line J774.1

摘要

Leukocytes exhibit a number of voltage-dependent ionic conductances which may be related to such cellular processes as secretion, chemotaxis, and mitogenesis. Three different voltage-dependent potassium currents have been described in macrophages. Long-term cultured mouse macrophages exhibit an inward rectifying potassium current activating at potentials negative to -70 mV. An outward potassium current activating at potentials positive to -40 mV has been described in shorter-term cultures. In addition, a calcium-activated potassium current has been described in cultured macrophages from a variety of sources. Recent single-channel studies have demonstrated large conductance calcium- and voltage-activated potassium channels in cultured human macrophages and large conductance chloride-selective channels in mouse macrophages. In this study we used a whole-cell patch-clamp techniques to characterize both inward and outward voltage-dependent potassium conductances in J774.1 cells. These cells, derived from a mouse reticulum sarcoma have been extensively studied because they provide homogeneous populations that express many properties characteristic of macrophages, including receptor-mediated endocytosis, secretion of enzymes and immunomodulatory factors, and chemotaxis. In addition, the existence of variant clones defective in specifif functions may make them particularly useful in relating ionic conductances to macrophage function.