WHOLE-CELL CL- CURRENTS IN HUMAN NEUTROPHILS INDUCED BY CELL SWELLING

The properties of the conductive Cl- transport pathway underlying regulatory volume decrease (RVD) in human neutrophils were investigated using the whole cell patch-clamp technique. Cell swelling was induced during whole cell recordings by making the patch pipette solution hyperosmotic (approximately 20%) relative to the bath by addition of sucrose. Immediately after establishment of the whole cell configuration, no measurable Cl- currents were evident. Over a period of several minutes the outwardly rectifying Cl- current. that, developed displayed no apparent voltage dependence of activation and did not inactivate with time during voltage steps over the range of -80 to +80 mV. Reduction of Cl- currents by application of suction to the interior of the pipette implied that the swelling-induced Cl- channels are activated by membrane stretch. Based on reversal potential measurements, the volume-induced Cl- conductance was found to discriminate poorly among Cl-, Br-, I-, and NO3-, to possess a finite permeability to glucuronate (P(glucuronate)/P(Cl) approximately 0.1) and to be impermeable to cations. Single-channel conductance was estimated to be 1.5 pS from analysis of the variance of membrane current fluctuations. The activated Cl- currents were blocked by 100 muM of the compound MK-447 analogue A (inhibitor constant K(i) = 37 muM) and by 200 muM 3,5-diiodosalicylate, 500 muM 4-acetamido-4'-iodothiocyanostilbene-2,2'-disulfonic acid, and 200 muM UK-5099. These results suggest that the initial event triggering RVD in neutrophils may be activation of stretch sensitive Cl- channels in the plasma membrane.