Inhibition of atherosclerosis associated with reduction of arterial intramural stress in rabbits.

Atherosclerotic lesions commonly develop at arterial branch sites, which are also the sites of high arterial intramural stress produced by intraluminal pressure. We investigated the effect of reduced intramural stress on the development of atherosclerotic lesions. We exposed the origin of the left renal artery in five rabbits and the aortic bifurcation in another five, lowered the mean arterial pressure to 35 to 45 mm Hg, and poured a dental acrylic liquid around the branch to form a rigid cast. When the rabbits recovered and the arterial pressure increased to normal, the casts prevented the arteries from expanding, thereby maintaining a low intramural stress. These rabbits plus two unoperated, two sham-operated, two with silicone rubber casts placed at similar pressures, and four with casts placed at 95 mm Hg pressure were given a 2% cholesterol-enriched diet for 7 to 11 weeks, and then their arteries were examined. In all rabbits, atherosclerotic lesions developed at the origins of the intercostal, celiac, superior mesenteric, and both renal arteries, and at the aortic bifurcation, with these notable exceptions: no lesions developed at the origins of casted renal arteries or at the casted aortic bifurcations when the cast was placed at a low pressure. Measurements of the diameter and thickness of the aorta in the left renal branch and aortic bifurcation areas, with and without the casts, indicated that there was no significant narrowing of the aortic lumen or thinning of the aorta due to the cast. In conclusion, the inhibition of the development of atherosclerotic lesions appears to be associated with the reduction of arterial intramural stress.