A protein kinase G-sensitive channel mediates flow-induced Ca2+ entry intovascular endothelial cells

The hemodynamic force generated by blood flow is considered to be the physi ologically most important stimulus for the release of nitric oxide (NO) and prostacyclin (PGI(2)) from vascular endothelial cells (1). NO and PGI(2) t hen act on the underlying smooth muscle cells, causing vasodilation and thu s lowering blood pressure (2, 3). One critical early event occurring in thi s now-induced regulation of vascular tone is that blood flow induces Ca2+ e ntry into vascular endothelial cells, which in turn leads to the formation of NO (4, 5). Here we report a mechanosensitive Ca2+-permeable channel in v ascular endothelial cells. The activity of the channel was inhibited by 8-B r-cGMP, a membrane-permeant activator of protein kinase G (PKG), in cell-at tached membrane patches. The inhibition could be reversed by PKG inhibitor KT5823 or H-8. A direct application of active PKG in inside-out patches blo cked the channel activity. Gd3+, Ni2+, or SK&F-96365 also inhibited the cha nnel activity. A study of fluorescent Ca2+ entry revealed a striking pharma cological similarity between the Ca2+ entry elicited by flow and the mechan osensitive Ca2+-permeable channel we identified, suggesting that this chann el is the primary pathway mediating flow-induced Ca2+ entry into vascular e ndothelial cells.