Tran C D, Butler R N, Howarth G S, Philcox J C, Rofe A M, Coyle P
Dept. of Physiology, The University of Adelaide, Institute of Medical and Veterinary Science, SA, Australia.
Scand J Gastroenterol. 1999 Jul;34(7):689-95. doi: 10.1080/003655299750025895.
Zinc (Zn) is protective and enhances epithelial repair in gut diseases. In this study we investigate the localization and distribution of Zn and its binding protein, metallothionein (MT), in the gut of rats fed diets varying in Zn content.
Male-Sprague Dawley rats were fed low, normal, high, or excess Zn in their diets (10, 100, 400, or 1000 mg Zn/kg, respectively) and killed 7 days later. Blood, liver, and gut tissues were collected. Tissue Zn was determined with atomic absorption spectrophotometery and MT with a Cd/haem affinity assay. Zn and MT were immunohistochemically localized in the small-intestinal wall with zinquin and an anti-MT antibody.
Most Zn in the intestinal wall was present in the mucosal scrapings, with 94% membrane-bound and 6% cytosolic, irrespective of dietary Zn. MT levels increased in all gut regions at dietary Zn levels above 100 mg Zn/kg. MT was 40% higher in the ileum than in other gut regions in rats fed low- and normal-Zn diets. The Zn content of the ileum was also 20% higher than that of other gut regions in rats fed low-, normal-, or high-Zn diets. Zn and MT were colocalized in the base of the intestinal crypts, most visibly in the ileum.
Mucosal cytosolic Zn and MT concentrations are increased only at high or excessive Zn intakes in all gut regions except the ileum, which can respond to a lower Zn intake. As the cytosolic Zn pool most likely influences mucosal protection and repair mechanisms, it is proposed that an increased MT may indicate the adequacy of oral Zn therapy in gut disease.
锌（Zn）具有保护作用，并能促进肠道疾病中的上皮修复。在本研究中，我们调查了喂食不同锌含量饮食的大鼠肠道中锌及其结合蛋白金属硫蛋白（MT）的定位和分布。
将雄性斯普拉格-道利大鼠分别喂食低、正常、高或过量锌的饮食（分别为10、100、400或1000 mg锌/千克），7天后处死。采集血液、肝脏和肠道组织。用原子吸收分光光度法测定组织锌含量，用镉/血红素亲和测定法测定MT含量。用锌喹和抗MT抗体通过免疫组织化学方法在小肠壁中定位锌和MT。
无论饮食锌含量如何，肠壁中的大多数锌都存在于黏膜刮片中，94%与膜结合，6%存在于细胞质中。当饮食锌水平高于100 mg锌/千克时，所有肠道区域的MT水平均升高。在喂食低锌和正常锌饮食的大鼠中，回肠中的MT比其他肠道区域高40%。在喂食低锌、正常锌或高锌饮食的大鼠中，回肠的锌含量也比其他肠道区域高20%。锌和MT共定位于肠隐窝底部，在回肠中最为明显。
除回肠外，所有肠道区域的黏膜细胞质锌和MT浓度仅在高锌或过量锌摄入时增加，回肠对较低的锌摄入有反应。由于细胞质锌池最有可能影响黏膜保护和修复机制，因此有人提出MT增加可能表明肠道疾病中口服锌治疗的充分性。
