Basic Study on Non-Delipidemic Fractionation of Aortic Connective Tissue of Human and Experimental Atherosclerosis

Abstract

Non-defatted portion of each lyophilized human and experimental atherosclerotic aortae were fractionated sequentially into glycosaminoglycan, glycoprotein, collagen and elastin, a modified method of directly non-dellpidemic elastin fractionation (Kramsch's method). The cholesterol contents, composition offatty acids of cholesterol ester and the lipid composition i the nondelipidated fractions were determined. The following results were observed:1) The accumulation of cholesterol in the arch, thoracic and abdominal aortic elastin fraction (fr.)accounted for 60-90% of the sum of the total cholesterol content of each connective tissue. 2) The elasin-bound fr. was digested by treatment of Pancreatic elastase, and fractionated into supernatant (sup.) and precipitate(ppt.). and then the ratio of digested cholesterol value (sup./sup. ppt.) was found to be about 70-90%.3) The intimal elastin fr.and collagen fr. from atherosclerotic plaques contained mach more cholesterol ester than other fractions. While other frs. (glycosaminoglycan fr. and glycoprotein fr.) from various layers contained free fatty acids as the most lipid constituent. 4) Characteristic feature of fatty acid moieties of cholesterol ester in the elastin fr. may be in that the ratios of C18:2, C18:1 and C18:2 are markedly changed, while C16:0 remains constant. 5) The mode of lipid deposition in the arterial elastin fr. obtained from the experimental nimals (rabbits and rats) was similar to the phenomenon of lipid accumulation i the human atherosclerotic aorta. The present method allowed estimation of lipid deposition in a small sample of aorta (about 10-20 mg of dry weight), and the cholesterol content of the connective tissue fraction may thus be used as one of the biochemical therosclerotic indices, proving the degree of severity together with histopathological methods.