[Endothelial modulation of arterial smooth muscle reactions to biological amines and electrical stimulation]

The effects of 5-hydroxytryptamine (5-HT), noradrenaline (NA), acetylcholine (Ach), ATP and electrical stimulation (ES) were studied in isolated porcine epicardial coronary artery and the rat thoracic aorta preparations. A dose-dependent contraction of vascular smooth muscle (VSM) segments with endothelium in response to biological amines (10(-7)-10(-5) M) and ES (2-16 Hz, 20 msec, 50 V) was demonstrated. Removal of the endothelium abolished the dilatory effect of the ATP (10(-5) M), Ach (10(-7) M), but potentiated the constrictor responses of the VSM to 5-HT, NA, ES. The results corroborate the hypothesis that the endothelium-derived relaxing factor, first, promotes the effect of vasodilators and, second, limits the vasoconstrictory effect to endogenous neurohumoral stimuli and plays a major role in the protection against a vasospasm.