A test for passive absorption of glucose in yellow-rumped warblers and its ecological implications
A test for passive absorption of glucose in yellow-rumped warblers and its ecological implications
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DOI：
10.1086/639618
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发表时间：
1997-05-01
期刊：
影响因子：
--
通讯作者：
Karasov, WH
中科院分区：
文献类型：
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作者：
Afik, D;McWilliams, SR;Karasov, WH
在早期的研究中，我们发现黄腰莺在体外对D-葡萄糖的主动吸收率仅为整个动物水平葡萄糖吸收率的百分之几。在这里，我们使用药代动力学技术来测试大量的糖是否可以被动吸收。我们使用了黄腰莺（Dendroica coronata），以其季节性食果动物而闻名，自由地进食用天然存在的D-葡萄糖浓度配制的合成糊状物。禽类吸收醪液中89.8% +/-1.0%（SE）的D-葡萄糖。当喂食含有痕量标记的H-3 L-葡萄糖（不与肠Na+-葡萄糖协同转运蛋白相互作用的立体异构体）的相同麦芽浆时，血浆中出现H-3，表明葡萄糖的这种立体异构体被吸收。我们在药代动力学模型中使用血浆和排泄物中的H-3水平来计算L-葡萄糖提取效率（即，吸收的百分比）。被动吸收的L-葡萄糖的计算平均提取效率平均为91% +/-23%。我们发现相当多的被动吸收调和D-葡萄糖吸收的体外和体内结果，并与其他五种鸟类的结果一致。被动途径似乎为鸟类提供了一种吸收过程，该吸收过程对变化的管腔浓度迅速响应，并且在真实的时间内维持和调节能量上不昂贵，但可能需要付出代价。歧视性被动吸收可能会增加对毒素的脆弱性，从而限制觅食行为，限制饮食生态位的宽度。
In an earlier study, we found that yellow-rumped warblers had in vitro active uptake rates of D-glucose that were only a few percent of the glucose absorption rate achieved at the whole-animal level. Here we used a pharmacokinetic technique to test whether a substantial amount of sugar can be absorbed passively. We used yellow-rumped warblers (Dendroica coronata), known for their seasonal frugivory, freely feeding on a synthetic mash formulated with naturally occurring concentrations of D-glucose. Birds absorbed 89.8% +/- 1.0% (SE) of the D-glucose in the mash. When fed the same mash with trace-labeled H-3 L-glucose, the stereoisomer that does not interact with the intestinal Na+-glucose cotransporter, H-3 appeared in plasma, an indication that this stereoisomer of glucose was absorbed. We used H-3 levels in plasma and excreta in a pharmacokinetic model to calculate L-glucose extraction efficiency (i.e., the percent absorbed). Calculated mean extraction efficiency for the passively absorbed L-glucose averaged 91% +/- 23%. Our finding of considerable passive absorption reconciles the in vitro and in vivo results for D-glucose absorption and is in concert with results from five other avian species. The passive pathway appears to provide birds with an absorptive process that call respond quickly to changing luminal concentration and that is energetically inexpensive to maintain and modulate in real time but that may bear a cost. Less discriminate passive absorption might increase vulnerability to toxins and thus constrain foraging behavior and limit the breadth of the dietary niche.