【摘要】 应用同位素标记高密度脂蛋白₃（HDL₃）,探讨家兔主动脉平滑肌细胞HDL₃的结合部位及其影响因素。结果表明,在平滑肌细胞表面存在具有特异性、高亲和力的HDL₃受体(Bmax=0.31μg/mg细胞蛋白,KD=5.6×10^-8mol/L)。培养液中的高浓度apoA₁可抑制¹²⁵I-HDL₃结合量的50％;用大鼠抗apoA₂抗体封闭¹²⁵I-HDL₃,其结合量可下降70％,而¹²⁵I-HDL₃与胆固醇预孵育,其与平滑肌细胞的结合率不受影响,提示apoA₁在HDL₃与受体结合过程中起着主要作用。培养液的pH在6.0～8.0之间,不影响HDL₃的结合;HDL₃结合部位对胰酶和裂解蛋白酶（pronase）处理均不敏感,且不依赖于Ca²⁺;4℃时其结合量最大。这些特性均与LDL受体不同,提示在平滑肌细胞表面存在着不同于apoB、E、apoE受体的HDL₃受体。更多还原

【Abstract】 The characteristics of HDL3 binding sites on cultured smooth muscle cells originally isolated from rabbit aorta were studied with 125I-labelled rabbit HDL3. The results indicated that specific and high-affinity HDLs binding sites were present on the surface of smooth muscle cells (Bmax = 0.321μg/mg cell protein; KD = 5.6× 10-8mol/L), The presence of a high concentration of non-labelled apo A1 blocked the 125I-HDL3 binding rate by 50%.125I-HDL3 pretreated (blocked) with rat antirabbit apo A1 IgG lost up to 70% of its original binding activity. Additionally, rabbit apo A1 was isolated, purified and its amino acid composition analyzed. The binding rate of 125I-HDL3 to smooth muscle cells was not affected by the presence of various concentrations of cholesterol. It was also relatively unaffected by trypsin or pronase treatment and independent of Ca2+ concentration. The optimal temperature and pH were 4℃ and 2 respectively. All of these characteristics differ from those of the LDL receptors. These results suggest that apo A1 is a major ligand of HDL3 receptors.更多还原