Lipid accumulation and ultrastructural change within the aortic wall during early spontaneous atherogenesis.

To identify the initial period and type of lipid accumulation during spontaneous atherosclerosis, quantitative chromatographic profiles of major lipid classes in upper thoracic aortas (non-lesion areas) and celiac artery cushions (lesion areas) were obtained from atherosclerosis-susceptible White Carneau (WC) and atherosclerosis-resistant Show Racer (SR) pigeons from 1 day to 6 months of age. Thoracic aortas of WC and SR pigeons contained similar amounts of cholesterol, nonesterified fatty acids, triacylglycerols, cholesteryl esters, phospholipids, and hydrocarbon at each age studied. However, celiac sites in WCs contained more total lipid than corresponding SR sites at 6 weeks and 6 months of age. This initial increase at 6 weeks in WCs was characterized by invreased concentrations of nonesterified saturated fatty acids. By 6 months of age, WC celiac cushions had greater concentrations of each lipid class except hydrocarbon than did SR cushions. This initial lipid accumulation was accompanied by ultrastructural changes within the arterial wall, which included the presence of extracellular, vesiclelike structures and extensive accumulation of basal lamina-like material between cells. This material was not present in aortic regions that are not predisposed to lesion formation. This material increased by 6 months of age in the enlarging WC fibromuscular intimal cushions. These morphologic changes paralleled the quantitative lipid increases and represented the first morphologic changes detectable at this site. Age-related changes in arterial lipid content and ultrastructure in SRs are different from those related to early spontaneous atherogenesis in WCs.