[Role of mechanosensitivity of the endothelium in weakening of the vascular bed vasoconstriction].

The effect of control of arterial diameter by the shear stress at the endothelium on noradrenaline-induced constriction of femoral vascular bed was investigated in anaesthetised cats. We compared noradrenaline-induced responses during the perfusion of the hindlimb at a constant blood flow and at a constant pressure as vasoconstriction is accompanied by an increase in wall shear stress only in the former case. We found that the same concentration of noradrenaline at a constant flow caused an augmentation of vascular resistance that was considerably smaller than at a constant pressure perfusion. This difference was almost eliminated after either removal of the endothelium or selective impairment of the endothelial sensitivity to the shear stress. These findings demonstrate that the control of arterial smooth muscle tone at a constant blood flow by shear stress at the endothelium does weaken noradrenaline-induced vasoconstriction.