Endothelium-dependent flow-induced dilation of canine femoral and saphenous arteries.

We have characterized the dilation response to increased blood flow in the canine femoral and saphenous arteries. An arterio-venous shunt was created and changes in arterial diameter measured by sonomicrometer crystals. Increasing shunt flow approximately 10-fold caused a 9% increase in femoral and 15% increase in saphenous artery diameter. The dilation response consisted of a transient decrease in diameter, followed by a rapid dilation and a slow return to control when flow was decreased. The increased diameter was not a result of decreased transmural pressure or alterations in pulse pressure. After removing the endothelial cells, the vessels did not dilate to increased flow or topical acetylcholine (10(-5) M), but responses to norepinephrine (10(-5) M) and sodium nitroprusside (10(-4) M) were unaltered. Indomethacin, theophylline or propranolol did not affect the flow-induced dilation. Quinacrine, an inhibitor of phospholipase A2, attenuated the dilation response in a dose-dependent manner. We conclude that increased blood flow affects endothelial cells, causing an active dilation of arterial smooth muscle.