Swift L L, Padley R J, Getz G S
J Lipid Res. 1987 Feb;28(2):207-15.
The synthesis of apoB-100 and apoB-48 by rat liver was investigated by studying the apoB complement of very low density lipoproteins (VLDL) from hepatic perfusates and Golgi fractions. The relative amounts of apoB-100 and apoB-48 in perfusate and Golgi VLDL as determined by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis were similar to those in serum VLDL. To investigate the relative rates of synthesis of the VLDL B proteins, rats were injected intraportally with tritiated amino acid, and hepatic Golgi and serum VLDL were isolated from 7.5 to 120 min later. In hepatic Golgi VLDL, apoB-100 and apoE were maximally labeled at 15 min after the tritiated amino acid pulse. In contrast, VLDL apoB-48 attained maximum radioactivity at 30 min after isotope injection. In serum VLDL, apoB-100 and apoE were maximally labeled at 30 min post-isotope injection, while activity in apoB-48 peaked at 60 min. The data suggest that the synthesis of the B proteins and incorporation into rat liver nascent VLDL are independently regulated. The differential labeling patterns of the VLDL B proteins may be explained by an intracellular pool of apoB-48 that is larger than that of apoB-100. An alternative explanation of the results is that apoB-100 is a precursor to apoB-48.
通过研究来自肝脏灌流液和高尔基体组分的极低密度脂蛋白（VLDL）中的载脂蛋白B（apoB）成分，对大鼠肝脏中apoB - 100和apoB - 48的合成进行了研究。通过十二烷基硫酸钠（SDS）聚丙烯酰胺凝胶电泳测定的灌流液和高尔基体VLDL中apoB - 100和apoB - 48的相对含量与血清VLDL中的相似。为了研究VLDL B蛋白的相对合成速率，给大鼠门静脉注射氚标记的氨基酸，7.5至120分钟后分离肝脏高尔基体和血清VLDL。在肝脏高尔基体VLDL中，氚标记氨基酸脉冲后15分钟，apoB - 100和载脂蛋白E（apoE）被最大程度地标记。相比之下，VLDL apoB - 48在同位素注射后30分钟达到最大放射性。在血清VLDL中，apoB - 100和apoE在同位素注射后30分钟被最大程度地标记，而apoB - 48的活性在60分钟达到峰值。数据表明，B蛋白的合成以及掺入大鼠肝脏新生VLDL是独立调节的。VLDL B蛋白的差异标记模式可能由比apoB - 100更大的细胞内apoB - 48池来解释。对结果的另一种解释是apoB - 100是apoB - 48的前体。
