Topic
Zinc toxicity
About: Zinc toxicity is a research topic. Over the lifetime, 727 publications have been published within this topic receiving 34583 citations. The topic is also known as: zinc poisoning.
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TL;DR: Results suggest that an activation of some antioxidant enzymes was enhanced to counteract the oxidative stress induced by the two metals.
239 citations
TL;DR: Comparison of relative tolerance capacities of transgenic plants, overexpressing either glyoxalase I or II individually or together in double transgenics, evaluated in terms of various critical parameters such as survival, growth, and yield, reflected double trans genics to perform better than either of the single-gene transformants.
Abstract: We reported earlier that engineering of the glyoxalase pathway (a two-step reaction mediated through glyoxalase I and II enzymes) enhances salinity tolerance. Here we report the extended suitability of this engineering strategy for improved heavy-metal tolerance in transgenic tobacco (Nicotiana tabacum). The glyoxalase transgenics were able to grow, flower, and set normal viable seeds in the presence of 5 mm ZnCl2 without any yield penalty. The endogenous ion content measurements revealed roots to be the major sink for excess zinc accumulation, with negligible amounts in seeds in transgenic plants. Preliminary observations suggest that glyoxalase overexpression could confer tolerance to other heavy metals, such as cadmium or lead. Comparison of relative tolerance capacities of transgenic plants, overexpressing either glyoxalase I or II individually or together in double transgenics, evaluated in terms of various critical parameters such as survival, growth, and yield, reflected double transgenics to perform better than either of the single-gene transformants. Biochemical investigations indicated restricted methylglyoxal accumulation and less lipid peroxidation under high zinc conditions in transgenic plants. Studies employing the glutathione biosynthetic inhibitor, buthionine sulfoximine, suggested an increase in the level of phytochelatins and maintenance of glutathione homeostasis in transgenic plants during exposure to excess zinc as the possible mechanism behind this tolerance. Together, these findings presents a novel strategy to develop multiple stress tolerance via glyoxalase pathway engineering, thus implicating its potential use in engineering agriculturally important crop plants to grow on rapidly deteriorating lands with multiple unfavorable edaphic factors.
237 citations
TL;DR: It is suggested that excess Zn exerts its toxicity partially through disturbing nutrient balance and inducing oxidative stress in plants through the adaptive mechanism in Zn non-hyperaccumulator plants.
234 citations
TL;DR: The role and manifestations of zinc in the environment and its importance for human health and metabolism, as well as its physiological role are summarized.
Abstract: Zinc is a common element in human and natural environments and plays an important part in many biological processes. Zinc, which is defined as an essential trace element, or a micronutrient, is essential for the normal growth and the reproduction of all higher plants and animals, and of humans. In addition, it plays a key role during physiological growth and fulfills an immune function. It is vital for the functionality of more than 300 enzymes, for the stabilization of DNA, and for gene expression. This review summarizes the role and manifestations of zinc in the environment and its importance for human health and metabolism, as well as its physiological role. Toxicity, teratogenicity, carcinogenicity, and immunological functions of zinc are outlined with particular reference to the properties of zinc as an antioxidant, and its role in cancer prevention.
231 citations
TL;DR: It is suggested that the lack of a hepatic reservoir of zinc jeopardizes the developing kidney in the MT-null mice, which are more sensitive to dietary zinc restriction, and MT I and MT II can protect against both zinc deficiency and zinc toxicity.
Abstract: Metallothionein (MT)-bound zinc accumulates when animals are exposed to excess zinc and is depleted under conditions of zinc deficiency, suggesting that MT serves as a means of sequestering excess zinc as well as a zinc reservoir that can be utilized when zinc is deficient. To examine the importance of MT for these processes, mice with null alleles of both MT I and MT II genes were created and the zinc concentration and histological appearance of multiple organs assessed. At birth, the hepatic zinc concentration of these MT-null mice was lower than that of wild-type controls (0.27 +/- 0.02 vs. 0.65 +/- 0.11 micromol zinc/g tissue, P < 0.05). During the next 3 wk of suckling zinc-replete (95 micrograms zinc/g diet) dams, the hepatic zinc concentration of controls fell to 0.42 +/- 0.04 micromol/g but was unchanged in the MT-null mice (0.28 +/- 0.04 micromol/g). The most prominent histological anomaly observed at 3 wk of age was the presence of swollen Bowman's capsules in the kidneys of MT-null mice. When nursing MT-null dams were fed a severely zinc-deficient (1.5 microg/g) diet, kidney development in the MT-null pups was retarded as indicated by the retention of the nephrogenic zone and incomplete tubule development. We suggest that the lack of a hepatic reservoir of zinc jeopardizes the developing kidney in the MT-null mice. In addition to being more sensitive to dietary zinc restriction, MT-null mice are more sensitive to zinc toxicity. When adult mice were challenged with a ramping dose of zinc up to a total of 3700 micromol zinc/kg body weight, MT-null mice had a greater incidence of pancreatic acinar cell degeneration compared with control mice despite accumulating less zinc (2.72 +/- 0.46 vs. 1.23 +/- 0.52 micromol zinc/g pancreas, control and MT-null, respectively, P < 0.05). The results of these experiments suggest that MT I and MT II can protect against both zinc deficiency and zinc toxicity.
224 citations