Pickel V M, Nirenberg M J, Chan J, Mosckovitz R, Udenfriend S, Tate S S
Department of Neurology and Neuroscience, Cornell University Medical College, New York, NY 10021.
Proc Natl Acad Sci U S A. 1993 Aug 15;90(16):7779-83. doi: 10.1073/pnas.90.16.7779.
A sodium-independent neutral and basic amino acid transporter (NBAT) from rat kidney was recently cloned and its amino acid sequence deduced. We used light and electron microscopic immunoperoxidase labeling to determine the cellular localization of NBAT in rat kidney and small intestine. The localization was carried out using site-directed antisera raised against synthetic peptides within NBAT. The most prominent localization of NBAT was in microvilli of epithelial cells lining renal proximal tubules. Microvilli of small intestinal epithelia were less frequently immunoreactive. Unexpectedly, the most intense labeling in the small intestine was seen within enteroendocrine cells and submucosal neurons. The neuronal labeling was highly localized within dense core vesicles in axon terminals apposed to the basal lamina near fenestrated blood vessels. These results support the proposal that NBAT plays a role in reabsorption of amino acids in renal tubules. In addition, they suggest that NBAT (or NBAT-like proteins) may have multiple functions in the small intestine, including luminal uptake of amino acids and vesicular uptake of related substrates into enteroendocrine cells and enteric neurons.
最近克隆了大鼠肾脏中的一种不依赖钠的中性和碱性氨基酸转运体（NBAT），并推导了其氨基酸序列。我们使用光镜和电镜免疫过氧化物酶标记法来确定NBAT在大鼠肾脏和小肠中的细胞定位。使用针对NBAT内合成肽产生的定点抗血清进行定位。NBAT最显著的定位是在肾近端小管内衬上皮细胞的微绒毛中。小肠上皮的微绒毛免疫反应性较低。出乎意料的是，在小肠中最强烈的标记出现在肠内分泌细胞和黏膜下神经元内。神经元标记高度定位于与有孔血管附近基膜相邻的轴突终末的致密核心囊泡内。这些结果支持了NBAT在肾小管氨基酸重吸收中起作用的观点。此外，它们表明NBAT（或NBAT样蛋白）可能在小肠中具有多种功能，包括腔内氨基酸摄取以及相关底物向肠内分泌细胞和肠神经元的囊泡摄取。
