BIOASSAY OF ENDOTHELIUM-DERIVED HYPERPOLARIZING FACTOR

Endothelium-derived hyperpolarizing factor (EDHF) mediates vasodilatat ion in certain blood vessels, together with prostacyclin and NO. Howev er, its chemical nature is not known. A perfusion-superfusion cascade was developed to confirm the diffusible nature of EDHF. Canine carotid arteries with endothelium were used as donors of vasoactive substance s, whereas rings of coronary artery without endothelium were used as d etectors. Inhibitors of NO synthesis and cyclooxygenase were present t hroughout, to avoid interference from NO and prostanoids. Measurements of membrane potential and isometric tension, in coronary arteries wit hout endothelium (used as detectors), demonstrated the release of EDHF from the carotid arteries, following treatment with 8-methoxypsoralen , bradykinin and thimerosal. The K+-channel blocker tetraethylammonium inhibited the action of EDHF in the detectors. Thus, these results de monstrate that endothelial cells release a diffusible activator of K+- channels in vascular smooth muscle. (C) 1996 Academic Press, Inc.