ENDOTHELIUM-DERIVED HYPERPOLARIZING FACTOR - A KEY MEDIATOR OF THE VASODILATOR ACTION OF BRADYKININ

Bradykinin causes vasodilatation by stimulating the production of vaso dilator prostanoids and nitric oxide (NO). However, there is an additi onal component that is mediated by a diffusible endothelium-derived hy perpolarizing factor (EDHF). The non-selective inhibitor of arachidoni c acid metabolism eicosatetraynoic acid inhibits the EDHF-mediated com ponent of the relaxation to bradykinin. Therefore, EDHF may be an arch idonic acid metabolite. The diffusible nature of EDHF has been dispute d because of the inability to consistently detect the factor using per fusion bioassay techniques. However, administration of the acyltransfe rase inhibitor thimerosal facilitates the release of EDHF by endotheli al cells in culture. Further studies are warranted to identity EDHF an d explore further its functions in vasomotion.