A flow-activated chloride-selective membrane current in vascular endothelial cells.

Shear stress-induced activation of endothelial ion channels, one of the earliest responses to flow, is implicated in mechano-signal transduction that results in the regulation of vascular tone. The effects of laminar flow on endothelial membrane potential were studied in vitro using both fluorescent potentiometric dye measurements and whole-cell patch-clamp recordings. The application of flow stimulated membrane hyperpolarization, which was reversed to depolarization within 35 to 160 seconds. The depolarization was caused by a Cl(-)-selective membrane current activated by flow independently of the K(+) channel-mediated hyperpolarization. Thus, flow activated both K(+) and Cl(-) currents, with the net membrane potential being determined by the balance of the responses. Membrane potential sensitivity to flow was unchanged by flow preconditioning that elongated and aligned the cells.