Thrombosis and atherosclerosis: The organization of pulmonary thromboemboli in the pig Macroscopic observations, protein, DNA, and major lipids

In order to investigate the possible contribution of the lipids of organizing thrombi to those of atherosclerotic plaques, the organization of autologous pulmonary thromboemboli in 8–12 week old Yorkshire pigs was studied at intervals from 6 hours to 4 weeks. Thrombi were prepared in vitro in Chandler rotating loops.There was a considerable loss of protein and total lipid in the interval from 6 hours to 5 days. No subsequent total lipid accumulation occurred. DNA content did not alter significantly. Free cholesterol and phospholipids accounted for > 85% of the total lipid, and both decreased in concentration from 6 hours to 5 days. Cholesterol ester, triglycerides and free fatty acids each comprised < 5% of the total lipid at all periods of organization, during which small increases in these lipids occurred.Spontaneous aortic fatty streaks and fibrous plaques of 5–712 year old pigs contained greater amounts of total lipid, phospholipids, free cholesterol and particularly cholesterol ester than the organizing thromboemboli, in spite of the transformation of the latter into fibrofatty plaques at 3–4 weeks.This study indicates that pulmonary thromboemboli may organize into fibrofatty lesions with many morphological features of atherosclerotic plaques. However, the lipid profile of organizing thromboemboli did not evolve towards that characteristic of the atherosclerotic plaque, suggesting that plaque lipids are largely derived from a source other than that of organizing thrombi.