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.

Hydrogen sulfide alleviates zinc toxicity by reducing zinc uptake and regulating genes expression of antioxidative enzymes and metallothioneins in roots of the cadmium/zinc hyperaccumulator Solanum nigrum L.

Abstract: Zinc (Zn) is a toxic element for plant at high concentrations. As a biologically active gaseous molecule, hydrogen sulfide (H2S) regulates plant growth and development. The aim of this study is to reveal the ameliorative effects of H2S on the physiological and molecular responses of a hyperaccumulator to Zn toxicity. Growth analysis, biochemical and zymological methods, fluorescent microscopic imaging, western-blot and quantitative real-time PCR analysis were performed to investigate the roles of NaHS (a donor of H2S) on the cadmium (Cd)/Zn hyperaccumulator, Solanum nigrum L. H2S ameliorated excess Zn-induced growth inhibition, especially in roots. H2S decreased free cytosolic Zn2+ content in roots which was correlated well with the down-regulation of Zn uptake and homeostasis related genes expression. Besides, H2S further enhanced the expression of the metallothioneins (MTs). Moreover, Zn-induced oxidative stress was also alleviated by H2S. The alleviation of H2S on excess Zn toxicity in S. nigrum is presumably attributed to: (1) the decrease in Zn accumulation via down-regulation of Zn uptake and homeostasis related genes expression; (2) the enhancement in the expression of MTs which chelate excess Zn; (3) the change in the genes expression of antioxidative enzymes, leading to H2O2 reduction.

Influence of water chemistry on the acute toxicity of copper and zinc to the cladoceran Ceriodaphnia cf dubia.

Abstract: This study determined the influence of key water chemistry parameters (pH, alkalinity, dissolved organic carbon [DOC], and hardness) on the aqueous speciation of copper and zinc and its relationship to the acute toxicity of these metals to the cladoceran Ceriodaphnia cf dubia. Immobilization tests were performed for 48-h in synthetic or natural waters buffered at various pH values from 5.5 to 8.4 (other chemical parameters held constant). The toxicity of copper to C. cf dubia decreased fivefold with increasing pH, whereas the toxicity of zinc increased fivefold with increasing pH. The effect of DOC on copper and zinc toxicity to C. cf dubia was determined using natural fulvic acid in the synthetic water. Increasing DOC was found to decrease linearly the toxicity of copper, with the mean effect concentration of copper that immobilized 50% of the cladocerans (EC50) value 45 times higher at 10 mg/L, relative to 0.1 mg/L DOC at pH 6.5. In contrast, the addition of 10 mg/L DOC only resulted in a very small (1.3-fold) reduction in the toxicity of zinc to C. cf dubia. Copper toxicity to C. cf dubia generally did not vary as a function of hardness, whereas zinc toxicity was reduced by a factor of only two, with an increase in water hardness from 44 to 374 mg CaCO3/L. Increasing bicarbonate alkalinity of synthetic waters (30–125 mg/L as CaCO3) decreased the toxicity of copper up to fivefold, which mainly could be attributed to the formation of copper-carbonate complexes, in addition to a pH effect. The toxicity of copper added to a range of natural waters with varying DOC content, pH, and hardness was consistent with the toxicity predicted using the data obtained from the synthetic waters.

Zinc toxicity, zinc deficiency and zinc-copper interrelationship in Eimeria acervulina-infected chicks.

Abstract: Three experiments were conducted with young chicks to investigate the effect of duodenal coccidiosis caused by Eimeria acervulina infection on Zn toxicity, Zn deficiency and the interrelationship between Zn and Cu. The coccidial infection depressed both rate and efficiency of weight gain. Dietary Zn addition at 2000 mg/kg depressed performance only slightly, but the 4000 mg/kg reduced both gain and gain/feed markedly. The coccidial infection appeared to have an ameliorative effect on Zn toxicity as assessed by performance and by hematological parameters. Excess Zn (2000 and 4000 mg/kg) dramatically increased liver, pancreas and bone Zn levels. The coccidial infection, however, decreased tissue Zn levels. Copper toxicity caused by feeding 500 mg Cu per kilogram diet was exacerbated by E. acervulina infection. A Zn-Cu antagonism was observed in both control and in coccidiosis-infected chicks. Excess dietary Zn decreased tissue Cu deposition, but excess Cu did not affect tissue Zn deposition. Copper partially ameliorated Zn toxicity symptoms. The efficacy of Cu in overcoming the Zn-induced depressed hematological parameters, however, was enhanced slightly by coccidiosis. E. acervulina infection did not affect the chick's Zn requirement. Growth data were more reliable as indicators of the Zn requirement than were blood or bone parameters.

Zinc: biochemistry, physiology, toxicology and clinical pathology.

Abstract: Among the transition and group II elements the abundance of zinc in biology is second only to that of iron. It is present in and indispensable to all forms of life. Knowledge regarding the biological occurrence and function of zinc, the development of methods that permit its detection and those aspects of biochemistry which have allowed an appreciation of the manner in which it participates in generating biological specificity have grown exponentially in the last two decades. The recognition that zinc is an essential, coenzyme-like component of many enzymes, indispensable to their function, is reminiscent of the role of some vitamins. Technical advances in the isolation and characterization of enzymes in general and metalloenzymes in particular were basic to the rapid growth of zinc metallobiochemistry during the last two decades. Zinc is now known to be an integral component of a large variety of proteins and enzymes and, hence, the total zinc content of tissues cannot serve as a guide to the multiple functions of the metal. Zinc participates in a wide variety of metabolic processes including carbohydrate, lipid, protein and nucleic acid synthesis or degradation. Most recently, zinc proteins have been shown to be involved in the transcription and translation of the genetic material, perhaps accounting for its essentiality to all forms of life. A number of zinc proteins have been described whose function is not known as yet. Among these, the metallothioneins are prominent. They are widely distributed, of low molecular weight (approximately 6700), and their content of cadmium and/or zinc as well as sulfur is exceptionally high.(ABSTRACT TRUNCATED AT 250 WORDS)