Beutler K T, Pankewycz O, Brautigan D L
Center for Cell Signaling, University of Virginia, Health Sciences Center, Charlottesville 22908, USA.
Biol Trace Elem Res. 1998 Jan;61(1):19-31. doi: 10.1007/BF02784037.
Zinc (Zn) is recognized as an essential nutrient, and is added as a supplement to animal and human diets. There are claims that zinc methionine (ZnMet) forms a stable complex that is preferentially transported into tissues, and this has contributed to uncertainty about conflicting reports on the bioavailability of various Zn compounds. This study evaluated the cellular and intestinal uptake of inorganic and organic forms of Zn. Steady-state uptake of 65Zn by human intestine epithelial cells, and monkey kidney fibroblasts was not significantly different with zinc chloride (ZnCl2), ZnMet, or zinc propionate (ZnProp) (P > 0.05). Uptake of 65Zn from zinc chelated with EDTA was significantly lower (P < 0.01). In live mice, 65Zn uptake by perfused intestine and deposition in intestine and liver showed no significant difference between ZnCl2 and ZnMet. Equimolar [65Zn]methionine and zinc[35S]methionine were prepared according to a patented method that yields "complexed" Zn. Cellular uptake of the radiolabeled methionine was <0.1% of the radiolabeled Zn from these complexes, indicating separate uptake of the Zn and methionine. Gel filtration did not distinguish between 65Zn in ZnCl2, ZnProp, or reagent ZnMet, though feed-grade ZnMet containing >10% protein did give a higher-mol-wt form of 65Zn. Results of this study show equivalent uptake of Zn from inorganic and organic compounds, and support recent feed trials on Zn bioavailability.
锌（Zn）被认为是一种必需营养素，并作为补充剂添加到动物和人类饮食中。有人声称蛋氨酸锌（ZnMet）形成一种稳定的络合物，能优先转运到组织中，这导致了关于各种锌化合物生物利用度的相互矛盾报告存在不确定性。本研究评估了无机和有机形式锌的细胞摄取和肠道摄取情况。人肠上皮细胞和猴肾成纤维细胞对65Zn的稳态摄取，在氯化锌（ZnCl2）、ZnMet或丙酸锌（ZnProp）之间无显著差异（P>0.05）。与乙二胺四乙酸螯合的锌对65Zn的摄取显著较低（P<0.01）。在活体小鼠中，灌注肠对65Zn的摄取以及在肠和肝脏中的沉积，在ZnCl2和ZnMet之间无显著差异。根据一种能产生“络合”锌的专利方法制备了等摩尔的[65Zn]蛋氨酸和锌[35S]蛋氨酸。这些络合物中放射性标记蛋氨酸的细胞摄取量<放射性标记锌的0.1%，表明锌和蛋氨酸是分别摄取的。凝胶过滤无法区分ZnCl2、ZnProp或试剂ZnMet中的65Zn，不过蛋白质含量>10%的饲料级ZnMet确实产生了一种高分子量形式的65Zn。本研究结果表明无机和有机化合物中的锌摄取量相当，并支持了近期关于锌生物利用度的饲料试验。
