Diffusional support of arteries.

The relative role of the arterial lumen, adventitial vasa vasorum, and medial vasa vasorum in nutritional support of arteries is unclear. We have used a newly developed autoradiographic method to study diffusion of metabolically inert [14C]antipyrine into arteries to determine the relative importance of different pathways in nutritional support of arteries. [14C]antipyrine was homogenously distributed across the media of small arteries within 15 s, which indicates that diffusion into the central media was rapid. In the thoracic and abdominal aorta, levels of antipyrine were higher in the inner media (P less than 0.05) than in the middle of the media. Levels of antipyrine in outer media of the thoracic aorta (which has medial and adventitial vasa) were comparable to those observed in the inner media, but antipyrine levels were lower in outer than in inner media of the abdominal aorta (which has adventitial vasa only). Ligation of intercostal arteries, which are the source of medial vasa vasorum in the thoracic aorta, decreased diffusional support to the outer media of the thoracic aorta. We conclude that 1) diffusional support is more effective in thinner muscular arteries than in the aorta, 2) both luminal and abluminal sources of nutrition are important, particularly for the aorta, 3) vasa vasorum appear to be important for adequate diffusional support of the thoracic aortic media, and 4) medial vasa vasorum may be more effective than adventitial vasa vasorum in nourishing the aorta.