Volume-Sensitive Chloride Channels Do Not Mediate Activation-Induced Chloride Efflux in Human Neutrophils

Many agents that activate neutrophils, enabling them to adhere to venular walls at sites of inflammation, cause a rapid Cl− efflux. This Cl− efflux and the increase in the number and affinity of β2 integrin surface adhesion molecules (up-regulation) are all inhibited by ethacrynic acid and certain aminomethyl phenols. The effectiveness of the latter compounds correlates with their inhibition of swelling-activated Cl− channels (IClvol), suggesting that IClvol mediates the activator-induced Cl− efflux. To test this hypothesis, we used whole-cell patch clamp in hypotonic media to examine the effects of inhibitors of up-regulation on IClvol in neutrophils and promyelocytic leukemic HL-60 cells. Both the channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid and [3-methyl-1-p-sulfophenyl-5-pyrazolone-(4)]-[1,3-dibutylbarbituric acid]-pentamethine oxonol (WW781), a nonpenetrating oxonol, inhibited IClvol at concentrations similar to those that inhibit β2 integrin up-regulation. However, ethacrynic acid, at the same concentration that inhibits activator-induced Cl− efflux and up-regulation, had no effect on IClvol and swelling-activated Cl− efflux, providing evidence against the involvement of IClvol in the activator-induced Cl− efflux.