Volume- and calcium-activated chloride channels in human umbilical vein endothelial cells

AIM: To characterize the properties of chloride currents and its modulation in human umbilical vein endothelial cells(HUVEC). METHODS: Using whole-cell patch-clamp recording techniques. RESULTS: Exposure of HUVEC to 13.5% and 27% hypotonic solution (HTS) induced a current I-Cl,I- vol. This current was correlated with the changes in cell volume and showed a modest outward rectification. It was slowly inactivated at positive potential ( >50 mV), and it was time- and voltage independent in kinetics. The current densities (pA/pF) were 20 +/- 3 (13.5% HTS) and 58 +/- 4 (27% HTS, n = 7), respectively at +100 mV test potential. Applying GTP gamma s (300 mu mol.L-1) elicited a current similar to I-Cl,I- vol, while cAMP (0.5 mmol.L-1) had no effect on the current. Increase in [Ca2+](i), either by directly loading cells with high concentration of Ca2+ (CaCl2), or by perfusing vasoactive agonist ATP (10 mu mol.L-1), activated Icl, ca The current density was only (23 +/- 5) pA/pF (n = 8 cells). Such current was slowly activated at positive potential, inactivated quickly at negative potential, and showed strong outward rectification. Both currents were inhibited by DIDS and verapamil. Challenging a cell with elevated [Ca2+](i) and HTS activated I-Cl,I- vol on the top of I-Cl,I- Ca in the same cell, suggested coexistence of these two currents and that they were modulated by different ways. cAMP-regulated chloride channel and ClC (chloride channel family) channel were absent. CONCLUSION: HUVEC express two kinds of chloride channels, I-Cl,I- vol activated by change in cell volume and I-Cl,I- Ca by elevation of [Ca2+](i), respectively.