THE VOLUME-ACTIVATED CHLORIDE CURRENT IN HUMAN ENDOTHELIAL-CELLS DEPENDS ON INTRACELLULAR ATP

We have studied the effect of intracellular ATP on volume-activated Cl --currents in endothelial cells from human umbilical veins by means of the whole-cell patch-clamp technique. The run-down of this current in ruptured patches during repetitive applications of hypotonic solution s (HTS) could be significantly reduced if the cells were internally pe rfused with a pipette solution that contained 4 mmol/l ATP. This run-d own was much less pronounced if currents were recorded using nystatin- perforated patches. The amplitude of the current was drastically reduc ed and its activation became slower if the cells were superfused with a glucose-free medium with 1 mmol/l KCN. Adding 4 mmol/l ATP gamma S, a poorly hydrolyzable ATP-analogue, to the patch pipette prevented run down of the current during repetitive activations by HTS, even if the cells were superfused with glucose-free solution with 1 mmol/l KCN. It is concluded that activation of the mechanosensitive Cl- conductance in human endothelial cells requires the presence of intracellular ATP, but not its hydrolysis.