Quantitation of apolipoprotein B in aortas of hypercholesterolemic swine.

An electroimmunoassay has been developed to quantify apolipoprotein B (apoB) in samples of aorta from normolipemic and hypercholesterolemic (diet-induced) swine. Acceptability of the assay was demonstrated using tests for specificity, sensitivity, accuracy, and validity. Specific sites in the grossly normal aortic arch of hypercholesterolemic animals were macroscopically demarcated after the injection of the dye, Evans blue. These blue sites, previously shown to be regions of early lesion formation, contained significantly greater amounts of apoB than adjacent nonblue (white) zones. By contrast, in normolipemic swine no difference in apoB content was found between blue and white regions of the arch. Likewise, the apoB content did not differ among various white regions of grossly normal aortas of hypercholesterolemic swine when no lesions were present. Also, once gross lesions were found in white regions, the apoB content was at least as great as in blue regions. The differences in apoB content between lesioned and nonlesioned areas were greatest in the abdominal aorta. The results of this study are consistent with an enhanced interstitial accumulation of lipoproteins containing apoB, especially low-density lipoprotein, occurring prior to lesion formation in this experimental model.