As part of a muticenter study on atherosclerosis, we examine defined segments of thoracic and abdominal aortas from 118 white males, age 15–34 years, who died from external causes. One half o each aorta specimen was graded or lesions. Intima-media preparations were assayed for collagen an cholesterol in two standardized regions (dorsal and ventral) derived from the alternate half of each segment. Even though the mean extent of intimal surface involvement with raise lesions remained minimal (0–6%), the data revealed a remarkable transition in vessel wall chemistry over this time span. For example, the amount of collagen per unit surface area increases with age in all vessel segments except the ventral domain of the thoracic aorta. The amount of collagen as a percent of total vessel protein rises with age only in the ventral and dorsal regions of the abdominal aorta. Free and esterified cholesterol levels per unit surface area increase with age in all vessel segments. There is a significant correlation between collagen and esterified cholesterol per unit surface area in all vessel regions with the exception of the abdominal ventral segment. In the latter segment increases in collagen per unit surface area occur without a corresponding increase in cholesterol level suggesting that connective tissue proliferation may actually precede lipid deposition in the genesis of atherosclerosis. Esterified cholesterol is present at higher levels in the dorsal domains of the thoracic and abdominal aortas than in the ventral domains. These findings provide chemical data confirming that the dorsal domain is the most lesion-prone region of these vessel segments. The most pronounced changes in aorta chemistry become apparent in the 25–29 year age range. Thus, the results suggest that for white males, preventive measures for atherosclerosis such as dietary restrictions should be instituted at the beginning of the third decade.
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