Flow- and bradykinin-induced nitric oxide production by endothelial cells is independent of membrane potential

The objective of this study was to evaluate the role transmembrane potential plays in flow-induced nitric oxide (NO) production in endothelial cells (EC). NO production was monitored by measuring intracellular guanosine 3',5'-cyclic monophosphate (cGMP) and extracellular nitrite plus nitrate (NOx). Primary human umbilical vein endothelial cells (HUVEC) were exposed to laminar flow (22 dyn/cm(2)) of medium with 5.4 mM KCl (control medium) with or without 3 mM tetraethylammonium chloride (TEA) or 90 mM KCI (K+-rich medium). Bradykinin (BK) was added to time-matched stationary cultures to give a final concentration of 5 nM. With control medium, 30 s, 2 min, and 3 h of treatment with flow or 2 min of treatment with BK resulted in an approximately threefold increase in cGMP over stationary cultures. Depolarization with KCl or TEA did not influence cGMP production in flow-treated or stationary cultures. Flow of either control or potassium-rich medium resulted in an similar to 10-fold increase in average NOx production rate over 3 h compared with stationary cultures. Taken together these data indicate that neither membrane hyperpolarization nor normal membrane potential is necessary for flow- or BK- induced NO production by HUVEC.