VOLUME-ACTIVATED CL- CURRENTS IN DIFFERENT MAMMALIAN NONEXCITABLE CELL-TYPES

The existence and properties of volume-activated Cl- currents were stu died in 15 different cell types (endothelium: human umbilical vein, hu man aorta, bovine pulmonary artery; fibroblasts: Swiss 3T3, L, C3H 10T 1/2, and COS-1; epithelium: KB3, HeLa and A6; blood cells: RBL-2H3 and Jurkat; endothelioma cells derived from both subcutaneous and thymic hemangiomas; skin: IGR1 melanoma). Volume-activated Cl- currents with common characteristics, i.e. small conductance, outward rectification, higher permeability for iodide than for chloride and sensitivity to b lock by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) could be el icited in all cells. The block of this current by tamoxifen and dideox yforskolin is different for the various cell types, as well as the tim e course and the amplitude of the responses induced by repetitive appl ications of hypotonicity. Volume-activated Cl- channels with similar b iophysical properties are therefore widespread among mammalian cells. This may reflect either a single Cl- channel that is ubiquitously expr essed or a family of functionally related Cl- channels with cell speci fic expression patterns.