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首页> 外文期刊>Journal of Comparative Physiology, B. Biochemical, Systemic, and Environmental Physiology >L-glucose absorption in house sparrows (Passer domesticus) is nonmediated
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L-glucose absorption in house sparrows (Passer domesticus) is nonmediated

机译：麻雀（Passer domesticus）中的L-葡萄糖吸收是非介导的

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摘要

We previously demonstrated in intact house sparrows substantial absorption in vivo of L-glucose, the stereoisomer of D-glucose that is assumed not to interact with the intestine's D-glucose transporter. Results of some studies challenge this assumption for other species. Therefore, we tested it in vitro and in vivo, based on the principle that if absorption of a compound (L-glucose) is mediated, then absorption of its tracer will be competitively inhibited by high concentrations of either the compound itself or other compounds (e.g., D-glucose) whose absorption is mediated by the same mechanism. An alternative hypothesis that L-glucose absorption is primarily paracellular predicts that its absorption in vivo will be increased (not decreased) in the presence of D-glucose, because the permeability of this pathway is supposedly enhanced when Na+-coupled glucose absorption occurs. First, using intact tissue in vitro, we found that uptake of tracer-radiolabeled L-glucose was not significantly inhibited by high concentrations (100 mM) of either L-glucose or 3-O-methyl-D-glucose, a non-metabolizable but actively transported D-glucose analogue. Second, using intact house sparrows, we found that fractional absorption of the L-glucose tracer was significantly increased, not reduced, when gavaged along with 200 mM 3-O-methyl-D-glucose. This result was confirmed in another experiment where L-glucose fractional absorption was significantly higher in the presence vs. absence of food in the gut. The greater absorption was apparently not due simply to longer retention time of digesta, because no significant difference was found among retention times. Our results are consistent with the idea that L-glucose is absorbed in a non-mediated fashion, largely via the paracellular pathway in vivo.
机译：我们先前在完整的麻雀中证明了L-葡萄糖（D-葡萄糖的立体异构体，其不与肠道D-葡萄糖转运蛋白相互作用）的体内大量吸收。一些研究的结果对其他物种的这一假设提出了挑战。因此，我们基于以下原理在体外和体内进行了测试：如果介导化合物（L-葡萄糖）的吸收，那么高浓度的化合物本身或其他化合物会竞争性地抑制其示踪剂的吸收（ （例如D-葡萄糖），其吸收是通过相同的机制介导的。 L-葡萄糖吸收主要是细胞旁吸收的另一种假设预测，在D-葡萄糖存在的情况下，其在体内的吸收将增加（而不是减少），因为据推测，当Na +偶联的葡萄糖吸收发生时，该途径的渗透性会增强。首先，我们在体外使用完整的组织，发现高浓度（100 mM）的L-葡萄糖或3-O-甲基-D-葡萄糖（不可代谢）不会显着抑制示踪放射性标记的L-葡萄糖的摄取。但积极转运D-葡萄糖类似物。第二，使用完整的麻雀，我们发现当与200 mM 3-O-甲基-D-葡萄糖一起使用时，L-葡萄糖示踪剂的吸收分数显着增加，而不是减少。该结果在另一项实验中得到了证实，在有食物的情况下，肠内食物的L-葡萄糖分数吸收显着高于没有食物的情况。吸收的增加显然不是由于消化物的保留时间更长，因为在保留时间之间没有发现显着差异。我们的结果与L-葡萄糖主要通过体内的旁细胞途径以非介导的方式吸收的想法一致。

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