A proton-activated, outwardly rectifying chloride channel in human umbilical vein endothelial cells.

Extracellular acidic pH-activated chloride channel I(Cl, acid), has been characterized in HEK 293 cells and mammalian cardiac myocytes. This study was designed to characterize I(Cl,acid) in human umbilical vein endothelial cells(HUVECs). The activation and deactivation of the current rapidly and repeatedly follows the change of the extracellular solution at pH 4.3, with the threshold pH 5.3. In addition, at very positive potentials, the current displays a time-dependent facilitation. pH-response relationship for I(Cl,acid) revealed that EC(50) is pH 4.764 with a threshold pH value of pH 5.3 and nH of 14.545. The current can be blocked by the Cl(-) channel inhibitor DIDS (100 microM). In summary, for the first time we report the presence of proton-activated, outwardly rectifying chloride channel in HUVECs. Because an acidic environment can develop in local myocardium under pathological conditions such as myocardial ischemia, I(Cl,acid) would play a role in regulation of EC function under these pathological conditions.