Glucose transporter gene expression in lactating bovine gastrointestinal tract.
Glucose transporter gene expression in lactating bovine gastrointestinal tract.
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DOI：
10.2527/1998.76112921x
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发表时间：
1998-11
影响因子：
3.3
通讯作者：
Feng-Qi Zhao;E. Okine;Chris I. Cheeseman;Soraya P. Shirazi-Beechey;J. Kennelly
中科院分区：
文献类型：
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作者：
Feng-Qi Zhao;E. Okine;Chris I. Cheeseman;Soraya P. Shirazi-Beechey;J. Kennelly
泌乳奶牛从肠道以及可能从胃肠道 (GIT) 的各个部分吸收葡萄糖可能会产生深远的影响，因为葡萄糖或葡萄糖前体的可用性似乎是牛奶合成的限制因素。本文报道了泌乳牛瘤胃、瓣胃、皱胃、十二指肠、空肠、回肠和盲肠粘膜组织中 Na+/葡萄糖协同转运蛋白基因 (SGLT1) 的表达。在所有检查的 GIT 组织的聚腺苷酸化 RNA 以及瘤胃、胃瓣、十二指肠、空肠、回肠和盲肠的总 RNA 中检测到钠/葡萄糖协同转运蛋白 mRNA 转录本。这些组织中 SGLT1 mRNA 的分布模式与促进葡萄糖转运蛋白 GLUT5 的分布模式不同。在泌乳奶牛的小肠膜中也检测到钠/葡萄糖协同转运蛋白。小肠刷状缘膜囊泡的钠依赖性葡萄糖摄取可以分解为线性不可饱和（扩散）和可饱和、载体介导的成分。葡萄糖从空肠膜囊泡的扩散常数为18.3+/-2.1 pmol x mM(-1) x mg蛋白质(-1) x s(-1)。葡萄糖摄取的可饱和部分的Vmax为27.1+/-5.8 pmol x mg蛋白质(-1) x s(-1)，Km为0.12+/-.05 mM。在十二指肠中也发现了类似的运输动力学，而在回肠中则较少。这些数据表明，泌乳牛的胃肠道能够主动将葡萄糖从管腔转运穿过上皮细胞的刷状缘膜。此外，瘤胃、瓣胃和盲肠中相对较高丰度的 SGLT1 mRNA 可能意味着这些组织在葡萄糖的主动转运中具有新的功能和营养作用。
Absorption of glucose from the intestine and probably from various portions of the gastrointestinal tract (GIT) in lactating dairy cows can have profound implications because the availability of glucose, or glucose precursors, seems to be a limiting factor for milk synthesis. This article reports on the expression of the Na+/glucose cotransporter gene (SGLT1) in mucosal tissues from rumen, omasum, abomasum, duodenum, jejunum, ileum, and cecum of lactating cows. Sodium/glucose cotransporter mRNA transcripts were detected in polyadenylated RNA of all the GIT tissues examined and in total RNA from rumen, omasum, duodenum, jejunum, ileum, and cecum. The pattern of SGLT1 mRNA distribution in these tissues was different from that of the facilitative glucose transporter GLUT5. Sodium/glucose cotransporter protein was also detected in small intestinal membranes of lactating dairy cows. Sodium-dependent glucose uptake across small intestinal brush border membrane vesicles could be resolved into linear nonsaturable (diffusion) and saturable, carrier-mediated components. The diffusion constant of glucose from jejunal membrane vesicles was 18.3+/-2.1 pmol x mM(-1) x mg protein(-1) x s(-1). The saturable component of glucose uptake had a Vmax of 27.1+/-5.8 pmol x mg protein(-1) x s(-1) and a Km of .12+/-.05 mM. Similar transport kinetics were found in the duodenum, and they were less in the ileum. These data suggest that the GIT of lactating cows is capable of active transport of glucose from the lumen across the brush border membrane of the epithelial cells. In addition, the relatively high abundance of SGLT1 mRNA in the rumen, omasum, and cecum may imply new functional and nutritional roles for these tissues in the active transport of glucose.