Rodriguez Yoldi M C, Mesonero J E, Rodriguez Yoldi M J
Facultad de Veterinaria, Universidad de Zaragoza, Spain.
Biol Trace Elem Res. 1993 May-Jun;37(2-3):269-79. doi: 10.1007/BF02783801.
Zinc is an essential trace element for life. Many metalloenzymes involved in the metabolism of carbohydrates, lipids, protein, and nucleic acids require zinc for their functions. The aim of this study was to characterize how zinc acts on the intestinal amino acid absorption in rabbit. Results obtained show that zinc inhibits both L-threonine accumulation in the jejunum tissue, and mucosal-to-serosal transepithelial flux of this amino acid in a dose-dependent way. The inhibition does not increase by a 10-min previous intestinal exposure of the mucosa to the heavy metal, and is not reversed by washing the intestinal tissue with saline solution or 10mM EDTA, but is appreciably reversed with 10mM dithioerythritol. Zinc seems not to modify amino acid diffusion across the intestinal epithelium. The inhibition of intestinal amino acid transport by zinc seems to be of a competitive type, and appears to be a result of impairment of the active transport that is altered by its binding to proteins (prevailing to thiol groups) of the brush-border membrane of enterocytes.
锌是生命必需的微量元素。许多参与碳水化合物、脂质、蛋白质和核酸代谢的金属酶发挥功能都需要锌。本研究的目的是明确锌如何作用于家兔肠道氨基酸吸收。研究结果表明，锌以剂量依赖的方式抑制空肠组织中L-苏氨酸的积累以及该氨基酸从黏膜到浆膜的跨上皮转运。在黏膜预先暴露于重金属10分钟后，这种抑制作用并未增强，用生理盐水或10mM乙二胺四乙酸（EDTA）冲洗肠道组织也不能逆转这种抑制作用，但用10mM二硫苏糖醇可明显逆转。锌似乎不会改变氨基酸跨肠上皮的扩散。锌对肠道氨基酸转运的抑制作用似乎属于竞争性类型，并且似乎是由于其与肠上皮细胞刷状缘膜上的蛋白质（主要是巯基）结合而改变了主动转运，从而导致主动转运受损的结果。
