The location of lecithin:Cholesterol transacylase activity in the atherosclerotic arterial wall

Cholesterol esterification by lecithin cholesterol fatty acid transferase (acylase) was estimated in multiple layers of atherosclerotic human and rabbit aorta; lecithin-β-[1-¹⁴C]linoleic acid was used as substrate. Between 5 and 9 layers were obtained from the inside to the outside of the aortas; adjacent samples were examined histologically. Most transferase activity was located in the outer part of the atherosclerotic intima, but some was located in the inner media. Medial transferase activity must be derived from smooth muscle cells. Some activity in the atherosclerotic intima is probably located in lipid phagocytes; such cells are thought to be modified smooth muscle. The high activity in the outer part of the atherosclerotic intima may be partly due to the hyperplastic layer of smooth muscle cells in the zone.