树鼩高密度脂蛋白与动脉平滑肌细胞相互作用的关系研究

STUDY ON THE RELATIONSHIP OF INTERACTION BETWEEN HIGH DENSITY LIPOPROTEIN AND AORTIC SMOOTH MUSCLE CELLS IN TREE SHREWS

树高密度脂蛋白（ＨＤＬ）与培养的动脉平滑肌细胞（ＳＭＣ）的结合既呈饱和性也呈非饱和性，胆固醇刺激细胞后能增加结合率，胰酶消化作用对结合无明显影响，在细胞膜蛋白中未发现有ＨＤＬ的特异结合蛋白。ＳＭＣ膜蛋白合成抑制后细胞清除胆固醇的功能未受明显影响。实验结果提示：树动脉ＳＭＣ与ＨＤＬ之间可能既存在特异性的结合位点，也存在非特异性的结合，细胞膜上ＨＤＬ的特异结合位点可能不是典型的蛋白质。ＨＤＬ主要通过其亚成分ａｐｏＡＩ和磷脂的协同作用转运细胞膜上的胆固醇。

The binding rate between SMC and HDL was saturable at a concentration of <150μg/ml,competrtive by treating with 30-fold of unlabelled HDL,and up regulated by cholesterol. once the concentration of HDL was over 150μg/ml,the binding became unsaturable.Additionally when the membrane proteins of SMC and apolipoproteins in HDL had been partially digested with trypsin, however the binding efficiency between SMC and HDL was not decreased.No HDL specific binding protein has been detected in the plasma membranes of SMC,liver cells as well as the adrenal corticai cells by Wearern blot or ligand blot.The clearance rate of 3￣H-cholesterol in SMC could not be significantly increased by either apoAI or phospholipid (PL) alone,in comparing with the control of SMC with LPDS,while the liposome composed of both apoAI and phospholipid could remarkbly increase the clearance rate of 3￣H-cholesterol in SMC(3-fold) which showed similar effect as natural HDL.The clearance rate of 3￣H-cholesterol from the SMC whose syntheses of membrane proteins were inhibited beforehand with cycloheximide kept a similar result obtained from the cells without cycloheximide administration.The results suggest that the binding between HDL and SMC in tree shrews might not only be mediated by specific binding sites,but also by nonreceptor pathway.and it seems that both apoAI and phospholipid play,in coordination,a role in the process of cholesterol transfer from SMC to HDL in tree shrews.