QUANTITATIVE-ANALYSIS OF CANINE PLASMA-LIPOPROTEINS

A combined ultracentrifugation/precipitation method for the measuremen t of lipoprotein cholesterol concentrations was developed and validate d for use with canine plasma. Very low density lipoproteins (VLDL) wer e isolated by flotation ultracentrifugation and low density lipoprotei ns (LDL) separated from high density lipoproteins (HDL) by precipitati on with heparin-manganese chloride. Effective separation of these clas ses was confirmed by agarose gel electrophoresis of native lipoprotein s and by sodium dodecyl sulphate polyacrylamide gel electrophoresis of their apolipoprotein distributions. There was trace contamination of the LDL precipitate with HDL, but this represented less than 4 and 9 p er cent of the total plasma HDL in normo- and hypercholesterolaemic do gs, respectively. The intra-assay and interassay coefficients of varia tion for LDL- and HDL-cholesterol concentrations were between 3.3 and 6.9 per cent, and 7.2 and 9.0 per cent, respectively, for plasma chole sterol concentrations between 2.67 and 8.14 mmol/litre. The intra-assa y coefficient of variation for VLDL-cholesterol was 53.8 and 18.4 per cent at plasma cholesterol concentrations of 2.67 and 8.14 mmol/litre, respectively. The inter-assay coefficient of variation for VLDL was 2 2.5 per cent. Storage of plasma at -20-degrees-C for between two and e ight.weeks did not affect VLDL-cholesterol concentrations, but led to an increase in LDL-cholesterol and a decrease in HDL-cholesterol conce ntrations of approximately 10 per cent. The method described is approp riate for the measurement of lipoprotein concentrations in plasma from normo- and hypercholesterolaemic dogs, but samples should not be subj ected to prolonged storage before analysis.