Endothelium-dependent modulation of vascular tone and platelet function.

Endothelial cells exert potent effects on vascular tone and platelet activity by the release of autacoids. One of the functionally most important autacoids is the endothelium-derived relaxant factor (EDRF). It inhibits platelet and vascular smooth muscle activation by cGMP-dependent attenuation of the agonist-induced rise of intracellular free Ca2+. Recent experiments suggest that EDRF has a physiologic role in the control of the vascular tone of large arteries and resistance vessels. Furthermore, there is evidence that an impairment of EDRF release may be a significant pathophysiologic factor in myocardial ischaemia. Coronary vascular tone might be also affected by the endothelium-derived vasoconstrictor peptide, endothelin, but its significance for the control of coronary blood flow remains to be elucidated.