We investigated whether pannexin-1, a carbenoxolone-sensitive hemichannel activated in erythrocytes by swelling, could be activated by swelling stress and contribute to swelling-activated chloride currents (I-Cl,I-swell) in HEK-293 cells. We used ethidium bromide uptake as an index of pannexin-1 activation and activation as an index of plasma membrane stretching. activated by a hypotonic solution was reversible inhibited by carbenoxolone (IC50 98 +/- 5 mu M). However, the hypotonic solution that activated I-Cl,I-swell did not induce ethidium bromide uptake indicating that pannexin-1 was not activated by cell swelling. The mimetic peptide (10)panx1, a pannexin-1 antagonist, did not affect I-Cl,I-swell activation but completely inhibited the ATP-induced ethidium bromide uptake Coupled to P2X(7) receptors activation. We conclude that carbenoxolone directly inhibited I-Cl,I-swell independent of pannexin-1 and that pannexin-1 hemichannels are not activated by swelling in HEK-293 cells. (C) 2009 Elsevier Inc. All rights reserved.