The Natural History of Atherosclerosis

Abstract

In order to complete the fragmentary knowledge of the natural history of atherosclerosis, the authors examined the coronary arteries of 403 captive and 146 wild vertebrates living in freedom, as well as the aortas of 134 of them. In 88 of the captive animals and in 51 of the free individuals, lipidogram, total cholesterol, beta-cholesterol and cholesterol/phospholipid ratio were also determined. In this material, spontaneous atherosclerosis always developed in arteries already impaired by intimal sclerosis, and intimal sclerosis seems to be a basic condition for spontaneous atherogenesis. Lipid deposits were found in the intima of 29 per cent of the examined aortas, but coronary atherosclerosis was present in only 2 per cent of the captive specimens. The discovery of coronary atherosclerosis in free tunny fishes, caught in the Bay of Biscay, brings proof that atherosclerosis is neither the privilege of warm-blooded vertebrates nor a consequence of captivity. Unfortunately, the material collected does not permit even a rough estimate of the influence of captivity on the development of atherosclerosis. It was observed in any case that captivity significantly alters some aspects of the lipidic metabolism in animals, and especially the beta-lipoprotein levels as well as the beta-cholesterol fraction. Spontaneous atherosclerosis may develop in fishes living in their natural habitat, feeding on a diet rich in unsaturated fats; in captive birds whose dietary fats are mostly unsaturated (crane, tree duck, pelican); and in wild mammals whose diet is free of animal fats, in freedom as well as in captivity (deer, camel, tapir).