Aortic Arteriosclerosis in the Dog After Localized Aortic X-lrradiation

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Abstract
Localized segments of the abdominal aortas of 18 dogs were irradiated with 50-kv. x-rays in doses ranging from 1,500 to 5,500 r (at the ventral surface of the aorta), and were examined histologically at intervals ranging from 2 to 48 weeks after irradiation. Arteriosclerosis developed at the irradiated sites and was significantly more severe than that which occurred in nonirradiated control sites in the abdominal aorta. There was evidence that severity of arteriosclerosis increased with time following irradiation of the aorta. There was less pronounced arteriosclerosis after 3,000 to 5,500 r than after 1,500 to 2,500 r. It appeared that the larger doses of x-rays inhibited the full development of the late lesions, although presumably causing more initial primary damage. X-irradiation appeared to be followed by the development of arteriosclerotic lesions similar to those that occur naturally in old dogs. It is proposed that irradiation may selectively cause injury of the internal elastic membrane, and that this degenerative phenomenon is followed by the development of intimal fibrosis and plaque formation.