Effects of silencing or overexpression of ZIP3 and ZIP5 on zinc absorption as zinc sulfate or zinc proteinate and related gene expressions in primary duodenal epithelial cells of broilers

Three Experiments were conducted to explore whether zrt/irt-like protein 3 (ZIP3) and ZIP5 were directly involved in zinc (Zn) absorption as Zn proteinate with moderate chelation strength (ZnP M) in broiler primary duodenal epithelial cells. In Experiment 1, siRNAs against ZIP3 or ZIP5 were transfected into cells, and the most effective siRNA was selected. In Experiment 2, with or without the most potent siRNA, cells were exposed to a basal medium without Zn (Control) or added with 400 umol/L of Zn as Zn sulfate (ZnS) or ZnP M for 120 min. In Experiment 3, with or without the recombinant adenovirus plasmid encoding ZIP3 or ZIP5, cells were treated with the same mediums as in Experiment 2. The data from Experiment 1 demonstrated that the si-230/si-1384 was the most effective (P < 0.0001) in reducing ZIP3/ZIP5 mRNA expression. The results from Experiment 2 showed that ZIP3 silencing did not affect (P > 0.05) Zn absorption for the added ZnS, but decreased (P < 0.05) Zn absorption for the added ZnP M. The ZIP5 silencing reduced (P < 0.05) Zn absorption for the addition of either ZnS or ZnP M, where the decrease of Zn absorption was higher for ZnP M than for ZnS. The results in Experiment 3 showed that ZIP3 overexpression did not influence (P > 0.05) Zn absorption for the added ZnS, but increased (P < 0.05) Zn absorption for the added ZnP M. The ZIP5 overexpression promoted (P < 0.05) Zn absorption for the addition of either ZnS or ZnP M, but the promotion of Zn absorption was greater for ZnP M than for ZnS. Additionally, ZnP M enhanced (P < 0.05) ZIP3 or ZIP5 protein expression, and ZnS increased (P < 0.05) ZIP5 protein expression, regardless of ZIP3 or ZIP5 silencing or overexpression. It is concluded that both ZIP3 and ZIP5 directly participate in Zn absorption as ZnP M, and ZIP5 is also involved in Zn absorption as ZnS within the cells.