Simultaneous measurement of membrane capacitance and whole cell currents during cell swelling in macrovascular endothelium

We have used the whole-cell patch-clamp technique, combined with membrane capacitance (C-M) measurements to study the activation mechanism of swelling-induced Cl- currents in cultured endothelial cells from bovine pulmonary artery (CPAE cells). Changes in C-M during cell swelling were less than 2% of its initial value in isotonic solution in 77% of the cells (1.1 +/- 0.2%, n = 17). In the remaining 23% of the cells, changes in C-M ranged between 4 and 13%(10.6 +/- 0.0%, n = 5). Cell swelling activated in all cells an outwardly rectifying Cl- current, which was correlated with the changes in cell volume but not with the changes in C-M. The Cl- current was also not affected if vesicular transport was inhibited with brefeldin A, Current activation and deactivation preceded the changes in C-M in those cells where such changes have been observed. It is concluded that activation of the swelling-induced Cl- current in endothelial cells is not due to incorporation of ion channels by vesicle fusion.