Endothelium and blood flow mediated vasomotion in the conscious dog

Numerous in vitro studies have demonstrated the important role of the vascular endothelium on the vasoactivity of vascular smooth muscle. Experimentation, particularly in conscious animals, is required to study the integrated role of endothelium in the regulation of vascular tone. This article reviews some of the evidence demonstrating endothelium mediated vasodilation and inhibition of vasoconstriction by the endothelium in the chronically instrumented conscious animal. Furthermore, a role for endothelial cells has been shown in the mechanism of blood flow-mediated vasodilation. Finally, the endothelium, through elaboration of constricting factors, e.g., endothelin, can also induce potent vasoconstriction. In the conscious animal endothelin elicits markedly differing degrees of vasoconstriction among the various regional vascular beds.