Abstract:Aim To observe the effects of cholesterol-rich lipoproteins [β-very low density lipoprotein (β-VLDL), normal low density lipoprotein (n-LDL)and oxidized low density lipoprotein(ox-LDL)] on lipid accumulation in smooth muscle cells (SMCs) and to explore its mechanism . Methods β-VLDL, n-LDL or ox-LDL was incubated with rabbit aortic SMCs for 48 hours, total cholesterol(TC)and triglyceride(TG)of the cells were extracted and determined. The increasing concentrations of lactoferrin (specific ligand of LDL receptor-related protein ,LRP) were added withβ-VLDL, n-LDL or ox-LDL, respectively, in the culture and TC and TG of the SMCs were determined as above. SMCs were incubated at 4℃ in M199 containing different concentrations of unlabeled lactoferrin and FITC-β-VLDL, FITC-n-LDL or FITC-ox-LDL, respectively, for 4 hours. The cell surface bound lipoproteins were determined by fluorospectrometry. Results β-VLDL, n-LDL and ox-LDL can all increase TC and TG accumulation in SMCs. More TC and TG were accumulated withβ-VLDL as compared with n-LDL or ox-LDL. The effects can be inhibited by lactoferrin. Moreover, lactoferrin competed with FITC-β-VLDL, FITC-n-LDL or FITC-ox-LDL on binding to SMCs. Conclusion β-VLDL, n-LDL and ox-LDL may contribute to lipid accumulation in SMCs by LRP mediated pathway.

Abstract:Aim We used hdgehogs to study the effects of low density lipoprotein-receptor inhibitor on the metabolism of low density lipoprotein and lipoprotein(a)with 125iodine.Methods Low density lipoprotein receptor inhibitor,Lactoferrin and receptor associated protein were used to inject into the body of hedgehogs via the armpit vein 2minites before the 125 iodine low density lipoprotein or 125 iodine lipoprotein (a) were injected.The animals were put to death in 6 h,The radioactivity in the blood,liver,kidney,spleen,gall and adrenal were measured;Results Experiments showed that the low density lipoprotein receptor were inhibited by lactoferrin and receptor associated protein。 The concentration of low density lipoprotein were decreased over 11.7%～86.7%in respectively compared with control group. However, the takeup of lipoprotein (a) in organs had not been inhibit ed,on the contrary it increases the takeup of lipoprotein (a) by the lactoferrin and receptor associated protein.The value of increasing was about 40%～120%。ConclusionsThe results indicated that lipoprotein (a)lose the capability to bind low density lipoprotein receptor since the configuration of lipoprotein (a) was changed in binding apolipoprotein(a)with apolipoprotein B100 although the construction and composition were similar with low density lipoprotein that they all contain the apolipoprotein B 100.It was inferred that lactoferrin and receptor associated ated protein could activite other mechanism on the cell membrane and favoured the lipoprotein(a)into the cells.