ENDOTHELIUM-DEPENDENT VASODILATORS DO NOT CAUSE PROPAGATED INTERCELLULAR CA2+ WAVES IN VASCULAR ENDOTHELIAL MONOLAYERS

Local application of a number of vasoactive agents affects vasomotor t one not only downstream to the point of application but also upstream. The mechanism(s) of upstream propagation is unknown. In endothelial c all monolayers, mechanical stimulation of one cell leads to intercellu lar propagation of increases In endothelial cell (EC) [Ca2+](i). In th is study, we tested whether increases in EC [Ca2+](i) induced by the l ocal application of the endothelium-dependent vasodilators ATP, bradyk inin and acetylcholine could spread across the monolayer. We demonstra te that unlike the response seen to a mechanical stimulus, there was n o significant propagation of increases in EC [CA(2+)](i) levels in res ponse to localized application of these agents. These findings suggest that upstream vasodilation in response to endothelium-dependent vasod ilators is not mediated by propagation of EC [Ca2+](i) waves and sugge st that other electrical or chemical signals are responsible.