Changes in rat serum lipoproteins following ligation of the bile duct

Lipoproteins in the serum of normal and of cholestatic rats have been studied by crossed immunoelectrophoresis coupled with separations by rate and isopycnic density gradient centrifugation and by gel exclusion chromatography. Normal rat serum contained distinct lipoprotein species closely analogous to human VLDL, LDL, HDL2 and HDL3. Three days after ligation of the common bile duct, there were major changes in the lipoproteins of rat serum. The amounts of VLDL, LDL and of a minor HDL component were elevated and several novel types of lipoprotein were detected. Three of these could be identified as the characteristic lipoprotein of cholestasis, LP-X, as an enlarged and modified HDL and as a lipoprotein of density 1.055 g/ml intermediate in size between LDL and VLDL. Some unusually small VLDL particles were also detected. It is concluded that the changes in rat serum lipoproteins following ligation of the common bile duct are very similar to the changes observed in cholestatic disease in human patients.