论文部分内容阅读
应用同位素标记高密度脂蛋白_3(HDL_3),探讨家兔主动脉平滑肌细胞HDL_3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HDL_3受体(Bmax=0.31μg/mg细胞蛋白,KD=5.6×10~(-8)mol/L)。培养液中的高浓度apoA_1可抑制~(125)I-HDL_3结合量的50％;用大鼠抗apoA_2抗体封闭~(125)I-HDL_3,其结合量可下降70％,而~(125)I-HDL_3与胆固醇预孵育,其与平滑肌细胞的结合率不受影响,提示apoA_1在HDL_3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HDL_3的结合;HDL_3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Ca~(2+);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HDL_3受体。
Isotope-labeled high-density lipoprotein-3 (HDL_3) was used to investigate the binding site of HDL_3 and its influencing factors in rabbit aortic smooth muscle cells. The results showed that HDL_3 receptor with specific and high affinity (Bmax = 0.31μg / mg cell protein, KD = 5.6 × 10 -8 mol / L) existed on the surface of smooth muscle cells. The concentration of apoA_1 in culture medium can inhibit 50% of the binding of 125 I-HDL_3, and the binding capacity of ~ 125 I-HDL_3 can be reduced by 70% Preincubation of I-HDL_3 with cholesterol and its binding to smooth muscle cells were unaffected, suggesting that apoA_1 plays a major role in the binding of HDL_3 to the receptor. The pH value of culture medium was between 6.0 and 8.0, which did not affect the binding of HDL_3. The binding site of HDL_3 was not sensitive to trypsin and pronase and did not depend on Ca ~ (2 +); The largest amount. These characteristics are different from those of LDL receptors, suggesting that HDL_3 receptors other than apoB, E and apoE receptors exist on the surface of smooth muscle cells.