Abstract: The tension of the vascular smooth muscle related with endothelium.two types of vascular strip were prepared from thoracic aorta of the rat. The vascular endotheium was intact in one group and removed in the other. The two types of preparations were superfused respectively with norepinephrine(1 μmol/L). The tension increment of vascular strip with intact endothelium was smaller than with removed endothelium.After washing away NE,the rate of the tension decrement with intact endothelium was more than that with removed endothlium.The two types of vascular strips after bathed in 10 % alcohol for one hour,were superfused respectively with NE,the tension increment with intact endothelium was more marked than without endothelium(P<0.05). Our data suggest that the active substance delivered by vascular endothelial cells not only influences the contraction process of smooth muscle,but also influences its the vasdilator process,and proteced the tension of vascular smooth muscle.

Key words: thoracic aorta, vascular endothelium, norepinephrine, the tension of vascular smooth muscle