Eisenberg S, Rachmilewitz D
J Lipid Res. 1975 Sep;16(5):341-51.
Incubation of 125I-labeled very low density lipoprotein (VLDL) with lipoprotein lipase-rich (postheparin) plasma obtained from intact or supradiaphragmatic rats resulted in the transfer of more than 80% of apoprotein C from VLDL to high density lipoprotein (HDL), whereas apoprotein B was associated with lipoprotein of density less than 1.019 g/ml (intermediate lipoprotein). The transfer of 125I-labeled apoprotein C from VLDL to HDL increased with time and decreased in proportion to the amount of VLDL in the incubation system. A relationship was established between the content of triglycerides and apoprotein C in VLDL, whereas the amount of apoprotein C in VLDL was independent of that of other apoproteins, especially apoprotein B. The injection of heparin to rats preinjected with 125I-labeled VLDL caused apoprotein interconversions similar to those observed in vitro. The intermediate lipoprotein was relatively rich in apoprotein B, apoprotein VS-2, cholesterol, and phospholipids and poor in triglycerides and apoprotein C. The mean diameter of intermediate lipoprotein was 269 A (compared with 427 A, the mean Sf rate was 30.5 (compared with 115), and the mean weight was 7.0 X 10(6) daltons (compared with 23.1 X 10(6)). From these data it was possible to calculate the mass of lipids and apoproteins in single lipoprotein particles. The content of apoprotein B in both particles was virtually identical, 0.7 X 10(6) daltons. The relative amount of all other constituents in intermediate lipoprotein was lower than in VLDL: triglycerides, 22%; free cholesterol, 37%; esterified cholesterol, 68%; phospholipids, 41%; apoprotein C, 7%, and VS-2 apoprotein, 60%. The data indicate that (a) one and only one intermediate lipoprotein is formed from each VLDL particle, and (b) during the formation of the intermediate lipoprotein all lipid and apoprotein components other than apoprotein B leave the density range of VLDL to a varying degree. Whether these same changes occur during the clearance of VLDL in vivo is yet to be established.
将125I标记的极低密度脂蛋白（VLDL）与从完整大鼠或膈上大鼠获得的富含脂蛋白脂肪酶（肝素后）的血浆一起温育，导致超过80%的载脂蛋白C从VLDL转移到高密度脂蛋白（HDL），而载脂蛋白B则与密度小于1.019 g/ml的脂蛋白（中间密度脂蛋白）相关联。125I标记的载脂蛋白C从VLDL向HDL的转移随时间增加，并与温育系统中VLDL的量成比例减少。在VLDL中甘油三酯含量与载脂蛋白C之间建立了一种关系，而VLDL中载脂蛋白C的量与其他载脂蛋白，尤其是载脂蛋白B的量无关。给预先注射了125I标记的VLDL的大鼠注射肝素，导致载脂蛋白相互转化，类似于在体外观察到的情况。中间密度脂蛋白相对富含载脂蛋白B、载脂蛋白VS-2、胆固醇和磷脂，而甘油三酯和载脂蛋白C含量较低。中间密度脂蛋白的平均直径为269 Å（与之相比，VLDL的平均直径为427 Å），平均Sf值为30.5（与之相比，VLDL的平均Sf值为115），平均分子量为7.0×10⁶道尔顿（与之相比，VLDL的平均分子量为23.1×10⁶）。根据这些数据，可以计算单个脂蛋白颗粒中脂质和载脂蛋白的质量。两种颗粒中载脂蛋白B的含量几乎相同，为0.7×10⁶道尔顿。中间密度脂蛋白中所有其他成分的相对含量均低于VLDL：甘油三酯为22%；游离胆固醇为37%；酯化胆固醇为68%；磷脂为41%；载脂蛋白C为7%，VS-2载脂蛋白为60%。数据表明：（a）每个VLDL颗粒仅形成一种中间密度脂蛋白；（b）在中间密度脂蛋白形成过程中，除载脂蛋白B外的所有脂质和载脂蛋白成分都不同程度地离开了VLDL的密度范围。这些相同的变化在体内VLDL清除过程中是否发生尚待确定。
