Endothelial mediators regulating vascular tonus]

Vascular endothelium is the unavoidable interface between blood and tissues. Its role as regulator of vascular tone is discussed here. The endothelium possesses different receptors for vasoactive mediators. These receptors activate the endothelial cells which in turn may produce secondary mediators acting on smooth muscle cells by activating or inhibiting their contraction. Such mediators are the endothelins which have a vasoconstrictor effect, and prostacyclin or endothelium-derived relaxation factors (EDRF) which have a vasodilator effect. Thus, the vascular endothelium and the mediators it secretes play a crucial role in vascular tone physiology.