Schonfeld G, Grimme N, Alpers D
J Cell Biol. 1980 Aug;86(2):562-7. doi: 10.1083/jcb.86.2.562.
Apoproteins have important physiologic functions in lipoprotein metabolism. Several apoproteins are produced in the intestine including ApoA-I, ApoA-IV, and ApoB. Each appears to participate in intestinal lipid transport. The liver also produces several apoproteins, including ApoC-II and ApoC-III, but the data demonstrating the ability of the intestine to produce ApoC is incomplete. Our aim was to ascertain whether ApoC-II and ApoC-III were present in human and rat jejunum, and if so, whether their presence was altered by fat feeding. The technique of immunolocalization and a newly developed double antibody radioimmunoassay for rat ApoC-III3 were used. ApoC-III3 was found in the supranuclear regions of enterocytes along the entire lengths of villi in the jejuna of 12-h-fasted rats. 1 hour after the gastric ingestion of corn oil. ApoC-III3 was found primarily in between cells and in the lamina propria. Similar results were obtained in human jejunal biopsies with ApoC-II and ApoC-III. ApoC-III3 was also detected by radioimmunoassay in enterocytes isolated from jejuna of neonatal and adult rats. Thus, ApoC-II and ApoC-III are clearly present in the intestine as well as in the liver. In addition, because their localization is altered after fat feeding, they are also likely to be produced in the enterocyte.
载脂蛋白在脂蛋白代谢中具有重要的生理功能。几种载脂蛋白在肠道中产生，包括载脂蛋白A-I、载脂蛋白A-IV和载脂蛋白B。每种载脂蛋白似乎都参与肠道脂质转运。肝脏也产生几种载脂蛋白，包括载脂蛋白C-II和载脂蛋白C-III，但关于肠道产生载脂蛋白C能力的数据并不完整。我们的目的是确定载脂蛋白C-II和载脂蛋白C-III是否存在于人和大鼠的空肠中，如果存在，其存在是否会因喂食脂肪而改变。使用了免疫定位技术和一种新开发的针对大鼠载脂蛋白C-III3的双抗体放射免疫分析法。在禁食12小时的大鼠空肠绒毛全长的肠上皮细胞的核上区域发现了载脂蛋白C-III3。在胃内摄入玉米油1小时后，载脂蛋白C-III3主要出现在细胞间和固有层。在人空肠活检中对载脂蛋白C-II和载脂蛋白C-III也得到了类似结果。通过放射免疫分析法在从新生大鼠和成年大鼠空肠分离的肠上皮细胞中也检测到了载脂蛋白C-III3。因此，载脂蛋白C-II和载脂蛋白C-III显然既存在于肠道也存在于肝脏中。此外，由于它们在喂食脂肪后定位发生改变，它们也可能在肠上皮细胞中产生。
