Na+-dependent intestinal glucose absorption mechanisms and its luminal Na+ homeostasis across metamorphosis from tadpoles to frogs
Na+-dependent intestinal glucose absorption mechanisms and its luminal Na+ homeostasis across metamorphosis from tadpoles to frogs
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蝌蚪到青蛙变态过程中Na依赖性肠道葡萄糖吸收机制及其管腔Na稳态
DOI：
10.1152/ajpregu.00249.2021
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Nozomi Nagata and Hisayoshi Hayashi
中科院分区：
文献类型：
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作者：
Noriko Ishizuka ,Mina Nagahashi ,Yuina Mochida ,Wendy Hempstock ;Nozomi Nagata and Hisayoshi Hayashi
在青蛙的变态过程中，肠道的突然形态变化已被详细描述。肠变态的特征是肠变短和肠上皮重塑。人们认为肠道形态变化的目的是为了适应从水生食草动物到食肉动物的生活。然而，对这些形态变化的生理重要性知之甚少。为了阐明蜕变过程中的功能变化，我们测量了蝌蚪和成年非洲爪蛙（xenopus laevis）的腔内Na+浓度和Na+依赖性葡萄糖摄取。分离小肠，按长度分成四段，取肠管内含量，用离子色谱法测定离子浓度。在装于Ussing室的肠制剂中测量了苯酞素敏感的葡萄糖诱导的短路电流（ΔIsc）。虽然蝌蚪的饮食钠摄入量极低，但肠道内钠离子浓度沿肠道近端至中部逐渐升高（约70 mM），与肉食性成年蛙相当。糖诱导蝌蚪肠道ΔIscwas升高。我们还用醋酸测定了ΔIscinduced，醋酸是发酵产生的主要短链脂肪酸。测定各肠段Na+依赖性葡萄糖转运蛋白1和紧密连接蛋白claudin-15 mRNA的表达水平。这些结果表明，在Na+依赖的营养吸收机制中，腔内Na+的稳态是重要的，保持腔内Na+的高浓度是重要的。
The abrupt morphological changes of the intestine during metamorphosis have been detailed in frogs. The features of intestinal metamorphosis are shortening of the intestine and remodeling of the intestinal epithelium. It is believed that the purpose of the morphological changes of the intestine is adaptation from aquatic herbivorous to carnivorous life. However, little is known about the physiological importance of these morphological changes. To elucidate the functional changes during metamorphosis, we measured luminal Na+concentrations and Na+-dependent glucose uptake in tadpoles and adult African clawed frogsXenopus laevis. The small intestine was isolated and divided into four segments in length, the luminal contents collected for analysis of ion concentration by ion chromatography. Phlorizin-sensitive glucose-induced short-circuit current (ΔIsc) was measured in intestinal preparations mounted in Ussing chambers. Although dietary sodium intake was extremely low in tadpoles, luminal Na+concentration gradually increased along the proximal to the middle part of the intestine (>70 mM), and this Na+concentration was comparable with that of carnivorous adult frogs. The increment of glucose-induced ΔIscwas observed in tadpole intestine. We also measured the ΔIscinduced by acetic acid, which is the major short-chain fatty acid produced by fermentation. The expression levels of mRNA for Na+-dependent glucose transporter 1 and tight junction protein claudin-15 in each intestinal segment was measured. These results suggest that luminal Na+homeostasis is important and luminal Na+is kept at a high concentration for Na+-dependent nutrient absorption mechanisms.