Crucial role of endothelium in the vasodilator response to increased flow in vivo.

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Abstract
Experiments were designed to investigate the importance of vascular endothelium in the vasomotor response to increases in flow as observed in conduit arteries (flow-dependent dilation). The diameter changes of femoral arteries (sonomicrometry) in response to increases in flow before and after endothelial damage procedures were studied in 23 dogs anesthetized with sodium pentobarbital. The functional integrity of the endothelial cells underneath the diameter sensors was tested by intra-arterial acetylcholine (local acetylcholine dilation) applied proximally to the sensors while a constant flow was maintained. Unilateral augmentation of femoral arterial flow (4.6 +/- 1.9-fold) induced by peripheral vasodilation or by arteriovenous shunt, elicited dilation (increase in diameter, 116 +/- 91 microns) in 18 of 23 dogs, whereas the diameter of the contralateral control artery was not affected. Mechanical removal of the endothelial cells by means of a balloon catheter abolished both the flow-dependent dilation an...