Diffusional support of the thoracic aorta in atherosclerotic monkeys.

We have demonstrated previously that there is increased blood flow through vasa vasorum in the aorta of atherosclerotic monkeys. In this study, a new method was used to examine diffusional support to the wall of blood vessels. Our goal was to determine whether proliferation of vasa vasorum in the outer media contributes to increased diffusional support of the atherosclerotic aorta and whether there are focal or homogeneous increases in diffusion to the aortic wall. Cynomolgus monkeys were fed normal or atherogenic diet for 1.5 or 4 years. Diffusional support of the thoracic aorta was determined by measuring the concentration of iodo[14C]antipyrine in the aortic media. The findings suggest that: 1) vasa vasorum provide only minimal nutritional support to the thoracic aorta of normal monkeys and monkeys with moderately severe atherosclerosis, and 2) in monkeys with severe atherosclerosis, diffusional support to the thoracic aorta is strikingly heterogeneous, ranging from minimal to large. We speculate that minimal diffusional support to the outer layers of the thickened atherosclerotic aorta may contribute to development of focal medial necrosis.