A role of the heavy subfraction of the floating lipids in acute alcoholic fatty liver of rats.

Two subfractions of floating lipids were studied to clarify the subcellular pathogenesis of ethanol-induced acute fatty liver in the rat. The main lipid in both the heavy and light subfraction was triglyceride, but the heavy subfraction was richer in phospholipids than the light subfraction. After ethanol-treatment of the animals, not only triglyceride but also phospholipids increased significantly in the light subfraction. The similarity of the phospholipid species in the two subfractions suggests a possible exchange of lipids between them. The heavy subfraction consisted of membrane-free lipid droplets of very low density lipoprotein (VLDL) size plus membrane-bound, vacuolated organelles; the light subfraction consisted of membrane-free lipid globules larger than 1000 nm in diameter. Occasionally adherent particles, 40 to 100 nm in diameter, were detected on the surface of the lipid globules. After ethanol treatment, the ratio of adherent particles to lipid globules increased significantly. These observations suggest that the biogenesis of acute alcoholic fatty liver in rats involves first the formation of membrane-free lipoproteins of VLDL size in the cytoplasm and subsequently their fusion to pre-existing lipid globules.