Comparison of lipoprotein fractionation by sequential density gradient ultracentrifugation with precipitation or fast phase liquid chromatography

Lipoprotein fractions, i.e. very low density (VLDL, rho =0.93-1.019), low d ensity (LDL, rho =1.019-1.063), and high density lipoprotein (HDL, rho =1.0 63-1.21) were separated by sequential gradient density ultracentrifugation (SDGU) and their cholesterol values were determined and compared with value s determined by fast phase liquid chromatography (FPLC) or HDL cholesterol by phosphotungstic acid-MgCl2 (PTMg) precipitation in hamsters fed diets co ntaining various levels of cholesterol. The correlation coefficient (r) for LDL between the SDGU and FPLC methods in plasma from hamsters fed 0 3% cho lesterol diets was 0.21-0.51, n=45. The FPLC method over estimated (+45%) L DL and the HDL values were under estimated (-18%). The agreement between FP LC and SDGU methods was also evaluated by plotting mean values against the differences between the values obtained by the two methods, FPLC method ove restimated LDL 22-49% (mean 36%) and HDL was underestimated 14-27% (mean 20 %). This was significant systematic bias with the FPLC method in VLDL, LDL and HDL values with the level of cholesterol in the diet. As FPLC is a fast method, it could be used in intervention type experiments to monitor the p rogress, however final results may need validation for research studies wit h the SDGU method. HDL determined by the SDGU method and phosphotungstic ac id MgCl2 precipitation in hamsters (n=26) fed 0.25% cholesterol diets was r epresented by two significantly different (P less than or equal to0.05) div ergent lines when a regression fitted model and a one-to-one relationship m odel by the two methods were plotted. The data su-cst that in hamsters fed either no added cholesterol or cholesterol-containing diets, lipoprotein fr actions determined by the precipitation method or by FPLC need to be valida ted against a SDGU for critical samples. Published by Elsevier Science Ltd.