Glickman R M, Kilgore A, Khorana J
J Lipid Res. 1978 Feb;19(2):260-8.
Monospecific antisera were produced to two chylomicron apoproteins (apoB, apoA-I) and utilized for indirect immunofluorescent localization of these apoproteins within rat intestinal epithelium during normal and impaired lipid absorption. Isolated intestinal epithelial cells prepared after different periods of lipid absorption from in situ intestinal segments revealed a rapid increase in fluorescence for both apoproteins that filled the entire apical portion of the cell. Prolonged lipid absorption for as long as 5 hr demonstrated sustained immunofluorescence and gave no indication of a depletion of the intestinal mucosa for either apoprotein during normal lipid absorption. [(3)H]Leucine incorporation into mesenteric lymph chylomicron apoproteins showed a linear decrease in specific activity of total chylomicron protein as well as apoB over 4 hr of a continuous lipid infusion indicating sustained active apoprotein synthesis during prolonged lipid absorption. Acetoxycloheximide, a potent inhibitor of protein synthesis, was employed to determine the dynamics of chylomicron apoproteins during an experimental condition of impaired lipid absorption. In animals with inhibited protein synthesis, fluorescence for both apoproteins was present early in the course of lipid absorption; however, at 60 min after the onset of lipid absorption, fluorescence for both apoproteins was absent. Fluorescence for both apoproteins returned during the recovery of protein synthesis. The present studies have confirmed previous results that localized two chylomicron apoproteins within intestinal epithelial cells. The present studies extend these observations and disclose a rapid and sustained synthesis of these apoproteins during prolonged chylomicron formation. During an experimental condition of impaired protein synthesis there was a marked reduction in the mucosal content of both apoA-I and apoB. These results are the first demonstration of impaired mucosal apoprotein synthesis during an experimental model of impaired lipid absorption.
制备了针对两种乳糜微粒载脂蛋白（载脂蛋白B、载脂蛋白A-I）的单特异性抗血清，并用于在正常和受损脂质吸收过程中，对这些载脂蛋白在大鼠肠上皮细胞内进行间接免疫荧光定位。从原位肠段吸收不同时间的脂质后制备的分离肠上皮细胞显示，两种载脂蛋白的荧光迅速增加，充满了细胞的整个顶端部分。长达5小时的延长脂质吸收显示出持续的免疫荧光，且在正常脂质吸收过程中，未显示出两种载脂蛋白中任何一种在肠黏膜中的消耗迹象。在连续脂质输注4小时期间，[³H]亮氨酸掺入肠系膜淋巴乳糜微粒载脂蛋白显示，总乳糜微粒蛋白以及载脂蛋白B的比活性呈线性下降，表明在延长的脂质吸收过程中载脂蛋白持续活跃合成。蛋白合成的强效抑制剂乙酰氧基环己酰亚胺被用于确定脂质吸收受损实验条件下乳糜微粒载脂蛋白的动态变化。在蛋白合成受抑制的动物中，两种载脂蛋白的荧光在脂质吸收过程早期就存在；然而，在脂质吸收开始后60分钟，两种载脂蛋白的荧光均消失。在蛋白合成恢复过程中，两种载脂蛋白的荧光又重新出现。本研究证实了先前将两种乳糜微粒载脂蛋白定位在肠上皮细胞内的结果。本研究扩展了这些观察结果，并揭示了在延长的乳糜微粒形成过程中这些载脂蛋白的快速和持续合成。在蛋白合成受损的实验条件下，载脂蛋白A-I和载脂蛋白B的黏膜含量均显著降低。这些结果首次证明了在脂质吸收受损的实验模型中黏膜载脂蛋白合成受损。
