Relationship between the cholesteryl esters and free cholesterol of individual atherosclerotic lesions and lesion size in aortas of rabbits on atherogenic and regression diets.

A study was made on the cholesterol lipids and DNA in lesions of aortas of rabbits either fed continuously on a cholesterol-rich diet or fed the cholesterol-rich diet for 6 weeks followed by a chow diet for up to 22 weeks. The DNA content of the aortic intimal-medial lesion samples was proportional to the surface area of these samples. The content of cholesteryl ester and unesterified cholesterol of the aortic lesions was compared with lesion area, lesion DNA and the topographical location on the thoracic and upper abdominal aorta luminal surface. The largest 80% of the lesions in an aorta contained a disproportionately large amount of cholesteryl ester compared to the smallest 20% of the lesions. The lesion content of free cholesterol compared to lesion area followed a nearly linear relationship. Similarly, cholesteryl ester content was non-linearly related to lesion DNA content but free cholesterol content was nearly proportionally related to DNA content. The non-linear relationships of cholesteryl ester content to lesion size and DNA content may be associated with a non-linear relationship between lipid inclusion volume and lesion size. The linearity observed for free cholesterol content as a function of lesion size may be due to a linear relationship between lipid inclusion surface area and lesion size. Neither diet nor the topographical location of lesions appeared to be important factors in affecting the cholesterol lipid content of lesions. Lesions became more irregular in shape as they grew larger.