Huff M W, Fidge N H, Nestel P J, Billington T, Watson B
J Lipid Res. 1981 Nov;22(8):1235-46.
The turnover and metabolism of the individual C apolipoproteins (C-II, C-III1, and C-III2) were studied following the injection of 125I-labeled VLDL into 15 normal and hyperlipoproteinemic subjects. The C apolipoproteins from very low density lipoprotein (VLDL) and high density lipoprotein (HDL) were separated by analytical isoelectric focusing, and subsequent densitometric scanning and radioassay of the stained bands yielded values for specific activity. In 13 of 15 subjects, kinetics of C-II, C-III1, and C-III2 were best described by a one-pool model, whereas two subjects showed biexponential kinetics. The specific activity-time curves for VLDL and HDL were super-imposable, indicating rapid exchange of all C apolipoproteins in hyperlipidemic as well as in normal subjects. In each subject the half-life was similar for C-II, C-III1, and C-III2, which suggests similar synthesis and catabolic mechanisms for each C apolipoprotein. The mass of exchangeable C-II (range 1.0-5.8 mg/kg), C-III1 (2.6-20 mg/kg), and C-III2 (2.0-13 mg/kg) increased with plasma triglyceride concentrations. Values for flux of C-II were 1.0-2.8 mg/d per kg, for C-III1 1.6-5.6 mg/d per kg, and for C-III2 1.2-3.1 mg/d per kg, but they were not related to levels of plasma triglyceride. However the irreversible fractional catabolic rates were inversely related to C apolipoprotein (and triglyceride) mass, suggesting that expansion in C apolipoprotein pool size is related to slower removal, due to the longer residence time of triglyceride-rich VLDL particles in plasma. This was confirmed by similar findings for B apolipoprotein kinetics in VLDL carried out simultaneously.
在向15名正常和高脂血症受试者注射125I标记的极低密度脂蛋白（VLDL）后，研究了个体载脂蛋白C（C-II、C-III1和C-III2）的周转和代谢。通过分析等电聚焦分离极低密度脂蛋白（VLDL）和高密度脂蛋白（HDL）中的载脂蛋白C，随后对染色条带进行光密度扫描和放射测定，得出比活性值。在15名受试者中的13名中，C-II、C-III1和C-III2的动力学最好用单池模型描述，而两名受试者表现出双指数动力学。VLDL和HDL的比活性-时间曲线相互重叠，表明高脂血症和正常受试者中所有载脂蛋白C都能快速交换。在每个受试者中，C-II、C-III1和C-III2的半衰期相似，这表明每种载脂蛋白C的合成和分解代谢机制相似。可交换的C-II（范围为1.0 - 5.8 mg/kg）、C-III1（2.6 - 20 mg/kg）和C-III2（2.0 - 13 mg/kg）的质量随血浆甘油三酯浓度增加。C-II的通量值为1.0 - 2.8 mg/（d·kg），C-III1为1.6 - 5.6 mg/（d·kg），C-III2为1.2 - 3.1 mg/（d·kg），但它们与血浆甘油三酯水平无关。然而，不可逆的分数分解代谢率与载脂蛋白C（和甘油三酯）质量呈负相关，这表明载脂蛋白C池大小的扩大与清除减慢有关，这是由于富含甘油三酯的VLDL颗粒在血浆中的停留时间更长。同时对VLDL中载脂蛋白B动力学的类似发现证实了这一点。
