Cardell R R, Badenhausen S, Porter K R
J Cell Biol. 1967 Jul;34(1):123-55. doi: 10.1083/jcb.34.1.123.
This report provides information on the morphology of fat absorption in rat intestinal epithelial cells. Three types of experiments were performed: (a) intubation of corn oil into fasted rats, (b) injection of physiological fatty-chyme prepared from fat-fed donor rats into ligated segments of jejunum of fasted animals, and (c) administration of electron-opaque particles in corn oil and markers given concurrently with the fat. These results support the hypothesis that fat is absorbed by selective diffusion of monoglycerides and fatty acids from micelles rather than by pinocytosis of unhydrolized triglycerides. Evidence is presented that the pits between the microvilli, previously believed to function in the transport of fat, are not involved in this process. Instead they appear to contribute their contents to lysosomes in the apical cytoplasm. Arguments are offered that the monoglycerides and fatty acids diffuse from the micelle while the latter is associated with the microvillous membrane of the absorptive cell. These micellar components penetrate the plasma membrane and diffuse into the cytoplasmic matrix where they encounter the SER. Triglyceride synthesis occurs in the SER and results in the deposition of fat droplets within its lumina. The synthesis of triglycerides and their sequestration into the SER establishes an inward diffusion gradient of monoglycerides and fatty acids.
本报告提供了大鼠肠道上皮细胞中脂肪吸收形态学的相关信息。进行了三种类型的实验：(a) 给禁食大鼠插管注入玉米油；(b) 将由喂食脂肪的供体大鼠制备的生理性脂肪乳糜注入禁食动物空肠的结扎段；(c) 在玉米油中给予电子不透明颗粒并与脂肪同时给予标记物。这些结果支持了以下假说：脂肪是通过单酰甘油和脂肪酸从微胶粒的选择性扩散而被吸收，而非通过未水解甘油三酯的胞饮作用。有证据表明，先前认为在脂肪转运中起作用的微绒毛之间的小窝并不参与此过程。相反，它们似乎将其内容物贡献给顶端细胞质中的溶酶体。有人提出，单酰甘油和脂肪酸在微胶粒与吸收细胞的微绒毛膜结合时从微胶粒中扩散出来。这些微胶粒成分穿透质膜并扩散到细胞质基质中，在那里它们遇到滑面内质网。甘油三酯的合成发生在滑面内质网中，并导致脂肪滴在其管腔中沉积。甘油三酯的合成及其在滑面内质网中的隔离建立了单酰甘油和脂肪酸的向内扩散梯度。
