Regulation of the zinc transporter ZnT-1 by dietary zinc

摘要

Using animal models, this study examined the pattern of expression of the Zn transporter, ZnT-1, in the intestine and the regulation of ZnT-1 by dietary Zn in the intestine and liver. Immunofluorescence demonstrated that intestinal ZnT-1 was most abundant at the basolateral surface of enterocytes lining the villi of the duodenum and jejunum. By Western blot analysis, intestinal and liver ZnT-1 protein migrated as a 42- and 36-kDa protein, respectively. Dietary Zn supplementation elevated the levelof intestinal ZnT-1 mRNA and protein approximately 50 and 10%, respectively, but had no effect in the liver. In response to an acute oral Zn dose, the level of intestinal ZnT-1 mRNA was up-regulated 8-fold, without a corresponding increase in ZnT-1 protein. Conversely, the acute oral dose did not affect liver ZnT-1 mRNA, but resulted in a 5-fold increase in liver ZnT-1 protein. The data suggest that ZnT-1 is at least part of the mechanism by which dietary Zn is absorbed and that, despite the Zn responsiveness of the ZnT-1 gene, additional factors may be regulating the steady-state level of ZnT-1 transporter protein.