the functional importance of endothelium-dependent dilatation is emphasized by the fact that the direct vasoconstrictor effects of some of these substances ( acetylcholine , histamine , norepinephrine , serotonin ) on vascular smooth muscle is attenuated or even reversed by their simultaneous stimulatory effect on endothelial cells resulting in the release of a vasodilator signal .
C0014257
endothelium
C0225336
endothelial cells