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Very los density lipoprotein (VLDL) was incubated with CuCl2(10 mumol/L) at room temperature for 24 hours. The thiobarbituric acid reactive substance (TBARS) was much higher and the electrophoretic mobility was much faster in VLDL after incubation with CuCl2 than that in VLDL without incubation with CuCl2. It demonstrated that VLDL was oxidatively modified by Cu2+. Endothelial cells were pretreated with normal VLDL (N-VLDL) and oxidatively modified VLDL (O-VLDL) and then the adhesion of monocyte to endothelial cells was assayed. We observed that O-VLDL at all the concentrations used enhanced monocyte adhesion to endothelial cells significantly. The results suggest that oxidative modification of VLDL may play a role in the early stage of atherogenesis by increasing monocyte adhesion to endothelial cells.

A highly sensitive and precise method for the determination of the polyamines (including putrescine, spermidine and spermine) in cell culture media is described. The samples were concentrated by C18 column and the polyamines were converted to fluorometric derivatives with DNS-Cl. The polyamine derivatives were then completely separated by HPLC and determined by simultaneous fluorometric detection. The CV of intragroup and intergroup were 2.49%-4.26% and 4.29%-5.16%, respectively. The rate of recovery was 103%-99%. There was trace amount of polyamines detected by this method in the media of F12, 8900, RPMI-1640, DMEM and M199 even without incubation with cells. So this method can be used for detecting the changes of polyamines in a medium before and after incubation with cells. It is helpful for the researches on the regulation of cell proliferation by polyamines.

A rapid method to obtain large amount of VLDL and LDL by ultracentrifugation is described. The mixture of VLDL and LDL was isolated and concentrated from plasma by an ultracentrifugation at 265 000 g for 2 h. VLDL and LDL were separated and purified by a further ultracentrifugation at 265 000 g for 3 h. This method combines the advantages of both sequential flotation ultracentrifugation and density gradient ultracentrifugation. It can process a large volume of plasma in a short time. The purity of isolated VLDL and LDL was confirmed by the lipoprotein electrophoresis on agarose gel and PAGE and by the apolipoprotein electrophoresis on SDS-PAGE. This rapid economical method is of great value in practical application.

Triglyceride was accumulated saturably in cultivated human fibroblasts exposed to increasing concentration of normal very low density lipoprotein (N-VLDL). Characterization of binding and degradation of 125I-N-VLDL by the cells indicated a direct uptake of intact N-VLDL particles via the cell surface receptor. Competition of unlabelled N-VLDL and LDL with 125I-N-VLDL in fibroblasts suggested that LDL receptor may be involved in this process. An unsaturable triglyceride accumulation in fibroblast induced by macrophage-conditioned medium containing N-VLDL was also observed. Intracellular triglyceride content, in this case, is linearly correlated with the concentration of N-VLDL in the medium and results mainly from re-esterification of fatty acid produced by hydrolysis of VLDL-triglyceride by lipoprotein lipase of macrophage.

It was demonstrated by using lipoprotein lipase (LPL) inhibitor benzene boronic acid (BBA) that LPL played a major role in the accumulation of triglycerides (TG) in mouse peritoneal macrophages exposed to rabbit normal very low density lipoproteins (N-VLDL). There wwere less free fatty acids (FFA) and much more N-VLDL-TG left in the media containing BBA than in the controls. TG accumulation in the cells was greatly diminished or even prohibited by BBA. Thus, we obtained direct evidence that LPL played a more important role than the receptor did in the uptake of N-VLDL-TG by mouse macrophages. The mechanisms of LPL action were discussed.

Rabbits were fed on 1% cholesterol and 10% rape seed oil (group A) or lard (group B). Plasma cholesterol and triglyceride level of group A was strikingly lower than that of group B. No difference was found in the lipid composition of beta-VLDLs between both groups. However, apo E content of beta-VLDL from group A was higher and apo B (higher molecular weight) was lower than that of group B respectively. beta-VLDL of group A caused greater accumulation of cholesterol in mouse peritoneal macrophage than that of group B. Therefore, we assume that the good effect of poly-unsaturated fatty acid on atherosclerosis results not from decreasing accumulation of cholesterol in macrophages but from enhancing elimination of beta-VLDL by the liver.