Endothelium-derived hyperpolarizing factor: a key mediator of the vasodilator action of bradykinin

Bradykinin causes vasodilatation by stimulating the production of vasodilator prostanoids and nitric oxide (NO). However, there is an additional component that is mediated by a diffusible endothelium-derived hyperpolarizing factor (EDHF). The non-selective inhibitor of arachidonic acid metabolism eicosatetraynoic acid inhibits the EDHF-mediated component of the relaxation to bradykinin. Therefore, EDHF may be an archidonic acid metabolite. The diffusible nature of EDHF has been disputed because of the inability to consistently detect the factor using perfusion bioassay techniques. However, administration of the acyltransferase inhibitor thimerosal facilitates the release of EDHF by endothelial cells in culture. Further studies are warranted to identify EDHF and explore further its functions in vasomotion.