Alterations in lipoprotein composition associated with galactosamine-induced rat liver injury.

The apoprotein and lipid composition and the morphology of lipoproteins was determined in rats with D-(+)-galactosamine (GalN) hepatitis. Single intraperitoneal injections of GalN at several dose levels and postinjection exsanguination times resulted in depressed levels of cholesteryl esters, an index of plasma lecithin:cholesterol acyltransferase (LCAT) activity, and increased levels of phospholipids, unesterified cholesterol, and triglycerides. Plasma withdrawn from rats 24 hr after injection of 1000 mg/kg GalN was most deficient in cholesteryl ester and was studied further by sequential isolation of VLDL, LDL, HDL1, HDL2, and HDL3. The increased plasma triglyceride (TG) after GalN treatment accumulated in TG-rich VLDL which contained two types of particles: a large (mean diameter 193.6 +/- 48.3 nm) and rough-edged particle, and a smooth one with a mean diameter (63.4 +/- 13.2 nm) similar to control VLDL (69.4 +/- 20.2 nm). The increased phospholiThe increased plasma triglyceride (TG) after GalN treatment accumulated in TG-rich VLDL which contained two types of particles: a large (mean diameter 193.6 +/- 48.3 nm) and rough-edged particle, and a smooth one with a mean diameter (63.4 +/- 13.2 nm) similar to control VLDL (69.4 +/- 20.2 nm). The increased phospholiThe increased plasma triglyceride (TG) after GalN treatment accumulated in TG-rich VLDL which contained two types of particles: a large (mean diameter 193.6 +/- 48.3 nm) and rough-edged particle, and a smooth one with a mean diameter (63.4 +/- 13.2 nm) similar to control VLDL (69.4 +/- 20.2 nm). The increased phospholipids and unesterified cholesterol were predominantly in LDL, HDL1, and HDL2 which were largely rouleaux of flattened vesicles. Density gradient ultracentrifugation of d greater than 1.006 g/ml lipoproteins confirmed these results. GalN hepatitis appeared to decrease the larger apoB335K subspecies and the apoC-III0 and apoC-III2 content of VLDL. However, total apoB concentration as GalN VLDL was increased 2.6-fold over control. LDL and HDL were markedly enriched in apoE. LDL apoB concentration was decreased by 41% while HDL was deficient in apoA-I, A-II and A-IV, and C. These results demonstrate association of increased plasma triglycerides with particles of grossly abnormal apoprotein composition, and the association of increased plasma phospholipids and unesterified cholesterol with apoE-rich lipoproteins during the LCAT defect produced by GalN hepatitis. These abnormal lipoproteins may represent an abnormal level of normal LCAT substrates important in the transport and esterification of plasma cholesterol.