Mansbach C M, Parthasarathy S
J Lipid Res. 1982 Sep;23(7):1009-19.
Conventional ideas concerning the unidirectional movement of triacylglycerol from intestinal lumen to lymph with sn-2-monoacylglycerol being the major glyceride-glycerol precursor were challenged by our finding that steady state specific activities of radiolabeled triacylglycerol (glyceryl moiety) in the intestinal mucosa and lumen were greatly reduced as compared to the specific activity of intraduodenally infused triacylglycerol. Investigation of the point at which the radiolabel was diluted was performed in mesenteric lymph duct-cannulated rats with a duodenal cannula through which trioleoyl[3H]glycerol was constantly infused. Both within the bowel lumen and in the intestinal mucosa, monoacylglycerol, diacylglycerol, and triacylglycerol specific activities were 31% or less of the specific activity of the infusate; chylomicron triacylglycerol specific activity was 75%. Efflux of neutral lipid from the mucosa into the bowel lumen was directly demonstrated by finding that when 3H glucose was injected intraperitoneally during triolein infusion, luminal triacylglycerol had a higher specific activity than was present in the mucosa. We conclude that there are two pools of mucosal triacylglycerol. One is rapidly transported and derives most of its glyceride-glycerol from luminal monoacylglycerol. The second is slowly transported; it derives its glyceride-glycerol mainly from endogenous sources and may efflux back into the bowel lumen.
传统观点认为三酰甘油从肠腔到淋巴呈单向移动，且sn-2-单酰甘油是主要的甘油酯甘油前体，但我们的研究结果对这一观点提出了挑战。我们发现，与十二指肠内注入的三酰甘油的比活性相比，肠黏膜和肠腔内放射性标记的三酰甘油（甘油部分）的稳态比活性大大降低。在肠系膜淋巴管插管的大鼠中进行了放射性标记稀释点的研究，通过十二指肠插管持续注入三油酰基[3H]甘油。在肠腔和肠黏膜内，单酰甘油、二酰甘油和三酰甘油的比活性均为注入液比活性的31%或更低；乳糜微粒三酰甘油的比活性为75%。通过发现在注入三油酸甘油酯期间腹腔注射3H葡萄糖时，肠腔三酰甘油的比活性高于黏膜中的比活性，直接证明了中性脂质从黏膜向肠腔的流出。我们得出结论，存在两个黏膜三酰甘油池。一个池快速转运，其大部分甘油酯甘油来自肠腔单酰甘油。第二个池转运缓慢；其甘油酯甘油主要来自内源性来源，可能会回流到肠腔中。
