Atherosclerosis and endothelium derived relaxating factor

We compared the vascular responsiveness in segments of thoracic aortas from control rabbits with the hypercholesterolmic and atherosclerotic rabbits which received cholesterol-rich diet for 16 weeks. The aortic arch and thoracic aorta were affected significantly more by lesions than the abdominal aorta. Segments of thracic aortas were mounted in organ chambers for isometric tension recording or for measurement of the endothelium derived relaxating factor, in rings of thoracic aortas, the relaxations to 10^-5 M acetylcholine, expressed as percent of the initial contraction caused by 2×10^-6 M norepinephrine, decreased from 82.5% in control tissues to 34.% in 16-weeks hypercholesterolemic vessels. The acetylcholine-induced release of endothelium derived relaxating factor from the thoracic aorta was significantly decreased by the hypercholesterolemia and atherosclrosis. The results suggest that the decrease of endothelium derived relaxating factor is mainly affected by the lesions of arteric endothelium in hypercholesterolemia.