Cigarette smoke and carbon monoxide do not have equivalent effects upon development of arteriosclerotic lesions

Experiments were performed to test whether exposure to mainstream cigarette smoke, without any diet modification, was sufficient to exacerbate arteriosclerotic lesion development in cockerels. Additionally, the experiments were designed to test whether any such effect could be attributed solely to carbon monoxide (CO) in the smoke. Three groups of cockerels (7/group) were exposed 5 days/week in standard inhalation chambers. Each day, one group (smoke) was exposed to smoke produced from the combustion of two packs of cigarettes. A second group (CO) was exposed to CO at levels equivalent to those produced during the combustion of two packs of cigarettes. A third group was sham-exposed. Following sacrifice, the abdominal aorta of each animal was cut into 5 mm segments and the extent of arteriosclerotic lesion development was measured. In smoke animals, compared to those in either of the other two groups, there were more aortic segments with measurable lesions present and the cross-sectional areas of these segments were greater. On a comparative basis, the smoke lesions were three times larger than in either of the other two groups, despite the fact that blood carboxyhemoglobin levels were the same in CO and smoke animals. The location of the lesions and their histological appearance were very similar to those previously described for spontaneous and carcinogen-associated lesions in the cockerel. These results demonstrate that as little as four months of daily exposure to cigarette smoke, in the absence of a cholesterol supplemented diet, can help accelerate arteriosclerotic lesion development. Further, this accelerated development cannot be attributed solely to CO in the smoke.