Binding of mercury in the rat: Studies using 203HgCl2 and gel filtration☆
01 May 1970-Toxicology and Applied Pharmacology (Toxicol Appl Pharmacol)-Vol. 16, Iss: 3, pp 743-753
TL;DR: In the kidney, with decreasing doses of mercury and prolonged survival time, the contribution of intermediate molecular weight protein complexes to the total 203Hg, as found with Sephadex G-200, tended to decline, and a relative increase was noticed in the fraction of the highest molecular weight as well as in the fractions of moderate molecular weight.
About: This article is published in Toxicology and Applied Pharmacology.The article was published on 1970-05-01. It has received 82 citations till now. The article focuses on the topics: Sephadex & Urine.
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TL;DR: The paper also touches on possible mechanisms for the "protective action" of selenium against mercury toxicity and deals briefly with the synergism between the two elements.
543 citations
Cites background from "Binding of mercury in the rat: Stud..."
...On the other hand, the mercury-metallothionein complex shows considerable stability and therefore causes long-term retention of mercury in the body (Jakubowski et al., 1970; Piotrowski et al., 1974)....
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TL;DR: Most of the bound Cd 2+ , which accumulates in the livers and kidneys of adult rats after the subcutaneous injection of CdCl 2 is recovered as a single, heat-stable fraction from the soluble components of these tissues, although this fraction in either organ also binds Zn 2+.
238 citations
TL;DR: Repeated administration of cadmium resulted in elevation of the concentration of metallothionein both in the liver and kidney, and this was confirmed by studying the incorporation of [ 14 C]-cysteine into the metallOTHionein fraction of proteins in vivo.
194 citations
TL;DR: It was concluded that Cd, Zn-thionein exists mainly as a random-coil peptide and as a model compounds for high-molecular-weight and water-soluble cysteine compounds, respectively.
Abstract: The preparation of pure metallothionein from Cd-pretreated rats and chicken was performed using short-time treatment with chloroform/ethanol followed by ion-exchange and gel chromatography. The protein contained 7 g-atoms metal ions per 12000 g protein. The Zn to Cd ratio was 1:2.4 ± 0.1. The Cd, Zn-thionein remained homogeneous during Sephadex G-25, G-50 and G-75 gel filtration, during polyacrylamide disc-gel electrophoresis and in the analytical ultracentrifuge. The high content of cysteine residues (approx. one-third of the total residues) was consistent with the cysteine content of metallothionein isolated from human or equine tissues. The Cd, Zn-thionein was of considerable temperature stability. The physicochemical properties were examined by ultraviolet spectroscopy, circular dichroism (CD) measurements and X-ray photoelectron spectroscopy. The millimolar absorption coefficient of the native protein was at 250 nm ɛ250= 80.6 mM−1· cm−1. Virtually no aromatic amino acids were present. The ɛ250 value of the apoprotein prepared by metal displacement using HCl was ɛ250= 13.2 mM−1· cm−1. When the ultraviolet spectrum of the apoprotein was recorded at pH 6.6 a distinct peak was detectable at 255 nm (ɛ250= 18.7 m M−1· cm−1). The existence of inter- or intramolecular disulphide formation was confirmed by CD measurements employing the polyethyleneglycol esters of di-tert-butyloxy-carbonyl-l-cystine and tert-butyloxycarbonyl-l-cysteine as model compounds for high-molecular-weight and water-soluble cysteine compounds, respectively.
From CD data it was concluded that Cd, Zn-thionein exists mainly as a random-coil peptide. Some indication of the binding of Cd and Zn in the native protein with ⊖S–R moieties was obtained from ultraviolet data. Final proof of the exclusive coordination of these metal ions with cysteine sulphur was successful using both circular dichroism measurements and especially X-ray photo-electron spectroscopy. The last method proved most convenient for determining the binding energies of the core electrons of Cd (Cd 3d3/2= 411.0 eV and Cd 3d5/2= 404.4 eV), Zn (2 p3/2= 1021.0 eV) and S (2p = 161.7 eV). The corresponding binding energies for S in the cystine complexes with Zn2+ and Cd2+ were 163.0 eV and 162.8 eV, respectively.
176 citations
TL;DR: In this article, the synthesis and degradation of rat liver metallothionein (MT) were investigated using 14C-cystine as precursor, Cd to stimulate the synthesis of this protein, and Sephadex G-75 chromatography as an isolation method.
156 citations
References
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Journal Article•
TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
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TL;DR: A discussion of predominantly theoretical aspects of metal poisoning is presented and the responses of biological systems to heavy metals were considered in terms of inferences that could be made concerning the site of the original chemical insult.
Abstract: A discussion of predominantly theoretical aspects of metal poisoning is presented. Heavy metals are capable of combining with a wide variety of organic molecules. The heavy metal binding was found to occur simultaneously at sensitive and insensitive sites. This diversion of the metals to insensitive sites protects the cell to some extent against the toxic action of metals, but at the same time tends to obscure the relation between metal binding and pharmacological response. The interactions of heavy metals with simple molecules, proteins, enzymes, cells, organs, and animals are reviewed. The responses of biological systems to heavy metals were considered in terms of inferences that could be made concerning the site of the original chemical insult. A listing and discussion of the most commonly seen responses are given. (M.C.G.)
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