Institute of Physiology and Zurich Center for Integrative Human Physiology , Zürich , Switzerland.
Department of Pediatric Surgery, Children's Hospital of Zürich , Zürich , Switzerland.
Am J Physiol Gastrointest Liver Physiol. 2018 Nov 1;315(5):G887-G895. doi: 10.1152/ajpgi.00318.2017. Epub 2018 Aug 30.
The expression of amino acid transporters in small intestine epithelia of human newborns has not been studied yet. It is further not known whether the maturation of imino acid (proline) transport is delayed as in the kidney proximal tubule. The possibility to obtain small intestinal tissue from patients undergoing surgery for jejunal or ileal atresia during their first days after birth was used to address these questions. As control, adult terminal ileum tissue was sampled during routine endoscopies. Gene expression of luminal imino and amino acid transporter SIT1 (SLC6A20) was approximately threefold lower in newborns versus adults. mRNA levels of all other luminal and basolateral amino acid transporters and accessory proteins tested were similar in newborn mucosa compared with adults. At the protein level, the major luminal neutral amino acid transporter BAT1 (SLC6A19) and its accessory protein angiotensin-converting enzyme 2 were shown by immunofluorescence to be expressed similarly in newborns and in adults. SIT1 protein was not detectable in the small intestine of human newborns, in contrast to adults. The morphology of newborn intestinal mucosa proximal and distal to the obstruction was generally normal, but a decreased proliferation rate was visualized distally of the atresia by lower levels of the mitosis marker K-67. The mRNA level of the 13 tested amino acid transporters and accessory proteins was nonetheless similar, suggesting that the intestinal obstruction and interruption of amniotic fluid passage through the small intestinal lumen did not affect amino acid transporter expression. NEW & NOTEWORTHY System IMINO transporter SIT1 is not expressed in the small intestine of human newborns. This new finding resembles the situation in the proximal kidney tubule leading to iminoglycinuria. Lack of amniotic fluid passage in small intestinal atresia does not affect amino acid transporter expression distal to intestinal occlusion.
尚未研究人类新生儿小肠上皮中氨基酸转运体的表达情况。此外，尚不清楚氨基酸（脯氨酸）转运的成熟是否像在肾脏近端小管中那样延迟。利用在出生后最初几天因空肠或回肠闭锁而行手术的患者获得小肠组织的可能性来解决这些问题。作为对照，在常规内镜检查期间从成人末端回肠组织中取样。与成人相比，新生儿的腔内腔氨基酸转运体 SIT1（SLC6A20）的基因表达大约低三倍。与成人相比，新生黏膜中所有其他腔内腔和基底外侧氨基酸转运体和辅助蛋白的 mRNA 水平相似。在蛋白质水平上，通过免疫荧光法显示主要的腔内腔中性氨基酸转运体 BAT1（SLC6A19）及其辅助蛋白血管紧张素转换酶 2在新生儿和成人中的表达相似。与成人相比，SIT1 蛋白在人新生儿的小肠中无法检测到。与成人相比，阻塞近端和远端的新生儿小肠黏膜的形态通常正常，但通过较低水平的有丝分裂标志物 K-67，在闭锁的远端可视化到增殖率降低。尽管如此，13 种测试的氨基酸转运体和辅助蛋白的 mRNA 水平相似，这表明肠梗阻和羊水通过小肠腔的中断并未影响氨基酸转运体的表达。新的和值得注意的是，系统 IMINO 转运体 SIT1 未在人新生儿的小肠中表达。这一新发现类似于近端肾小管中的情况，导致亚氨基甘氨酸尿症。羊水在小肠闭锁中不能通过不会影响肠闭塞后远端的氨基酸转运体表达。
