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

The properties of the conductive Cl- transport pathway underlying regu latory volume decrease (RVD) in human neutrophils were investigated us ing the whole cell patch-clamp technique. Cell swelling was induced du ring whole cell recordings by making the patch pipette solution hypero smotic (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 ap parent voltage dependence of activation and did not inactivate with ti me 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 membra ne stretch. Based on reversal potential measurements, the volume-induc ed Cl- conductance was found to discriminate poorly among Cl-, Br-, I- , and NO3-, to possess a finite permeability to glucuronate (P(glucuro nate)/P(Cl) approximately 0.1) and to be impermeable to cations. Singl e-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 c onstant K(i) = 37 muM) and by 200 muM 3,5-diiodosalicylate, 500 muM ac etamido-4'-iodothiocyanostilbene-2,2'-disulfonic acid, and 200 muM UK- 5099. These results suggest that the initial event triggering RVD in n eutrophils may be activation of stretch sensitive Cl- channels in the plasma membrane.