Tam S P, Dory L, Rubinstein D
J Lipid Res. 1981 May;22(4):641-51.
The apoprotein and lipid composition of HDL-like products arising from lipolysis of human VLDL was studied. The VLDL was perfused through beating rat hearts in the absence of serum to avoid possible alteration of the primary products of lipolysis due to apoprotein exchange with serum lipoproteins. The lipolytic products were separated by gel filtration to obviate possible losses of apoproteins from the lipoproteins during ultracentrifugation. Apoprotein B, E, C-II, and C-III were quantitated by electroimmunoassay and lipids were determined by chemical methods. During perfusion, a 50% hydrolysis of the VLDL triacylglycerols was associated with the appearance of 11% of the apoC-II, 30% of the apoC-III, and 20% of apoE of the VLDL in HDL-like particles as isolated by agarose gel filtration. The shift of the apoproteins to these particles was associated with a similar redistribution of cholesterol, phospholipid, and cholesteryl ester. The lipid composition of the HDL-like particles was cholesterol (15.1 +/- 4.0%), phospholipid (37.8 +/- 3.2%), cholesteryl ester (34.2 +/- 2.6%), and triglyceride (12.9 +/- 3.2%). The particles possessed a hydrated density of 1.063-1.21 g/ml and were spherical, with particle diameters (mean 124 +/- 36 A, range 50-160 A) that were comparable to the diameter (140 A) estimated from calculations of the surface to volume ratio, assuming a spherical particle consisting of a neutral lipid core surrounded by cholesterol, phospholipid, and protein. No discoidal forms or rouleau structures were observed in the HDL-sized fraction isolated by gel filtration. The HDL-like fraction could be resolved further by heparin-Sepharose chromatography into an unretained fraction containing predominantly apoC-III with apoE and apoC-II, and a retained fraction containing apoC-III and apoE. Small amounts of apoE were also recovered in extremely small particles that are normally observed in the d > 1.21 g/ml fraction after ultracentrifugation. No apoC-II or C-III was observed in this fraction. Incubation of VLDL with lipoprotein lipase, mobilized from hearts by heparin perfusion, yielded results that were similar to those with the perfused heart. Hearts perfused with VLDL removed apoB but not apoC-II, C-III, E, or phospholipids from the perfusate. It is concluded that the initial products of VLDL catabolism include spherical particles, similar in size to HDL, that contain apoC-II, C-III, E, cholesterol, cholesteryl esters, and phospholipids. ApoE is also released as a small extensively delipidated particle.-Tam, S. P., L. Dory, and D. Rubinstein. Fate of apolipoproteins C-II, C-III, and E during lipolysis of human very low density lipoproteins in vitro.
对人极低密度脂蛋白（VLDL）脂解产生的类高密度脂蛋白（HDL）产物的载脂蛋白和脂质组成进行了研究。在无血清条件下，将VLDL灌注到跳动的大鼠心脏中，以避免由于载脂蛋白与血清脂蛋白交换而可能改变脂解的初级产物。通过凝胶过滤分离脂解产物，以避免在超速离心过程中脂蛋白中的载脂蛋白可能损失。通过免疫电泳法定量载脂蛋白B、E、C-II和C-III，并通过化学方法测定脂质。在灌注过程中，VLDL三酰甘油50%的水解与HDL样颗粒中出现的11%的apoC-II、30%的apoC-III和20%的VLDL的apoE相关，这些颗粒通过琼脂糖凝胶过滤分离。载脂蛋白向这些颗粒的转移与胆固醇、磷脂和胆固醇酯的类似重新分布相关。HDL样颗粒的脂质组成为胆固醇（15.1±4.0%）、磷脂（37.8±3.2%）、胆固醇酯（34.2±2.6%）和甘油三酯（12.9±3.2%）。这些颗粒的水合密度为1.063 - 1.21 g/ml，呈球形，粒径（平均124±36 Å，范围50 - 160 Å）与根据表面积与体积比计算估计的直径（140 Å）相当，假设球形颗粒由中性脂质核心被胆固醇、磷脂和蛋白质包围。在通过凝胶过滤分离的HDL大小的级分中未观察到盘状形式或缗钱状结构。通过肝素 - 琼脂糖色谱法可将HDL样级分进一步分离为一个未保留级分，主要包含apoC-III以及apoE和apoC-II，和一个保留级分，包含apoC-III和apoE。在超速离心后通常在d＞1.21 g/ml级分中观察到的极小微粒中也回收了少量的apoE。在该级分中未观察到apoC-II或C-III。用肝素灌注从心脏动员的脂蛋白脂肪酶孵育VLDL，得到的结果与灌注心脏的结果相似。用VLDL灌注的心脏从灌注液中去除了apoB，但未去除apoC-II、C-III、E或磷脂。结论是，VLDL分解代谢的初始产物包括大小与HDL相似的球形颗粒，其含有apoC-II、C-III、E、胆固醇、胆固醇酯和磷脂。apoE也以一种高度脱脂的小微粒形式释放。- 谭，S.P.，L.多里，和D.鲁宾斯坦。人极低密度脂蛋白体外脂解过程中载脂蛋白C-II、C-III和E的命运
