Effect Of Zinc Ions Research Articles

Zinc-induced alterations in contractile properties of rat diaphragm muscle in vitro.

The effect of zinc ions on the isometric contraction of rat diaphragm muscles in the presence and in the absence of external calcium was studied. Using a transducer, the isometric force was measured as a function of supramaximal electrical stimulation, either directly or indirectly applied to the muscle. The following parameters were measured: peak twitch tension, PT, twitch contraction time, CT, relaxation half-time, RT-1/2, and peak rates of tension increase and decrease, +dP/dt and -dP/dt. The following zinc-induced alterations were observed: an increase of the PT; a decrease of the RT-1/2; an increase in the +dP/dt and -dP/dt. The CT was not changed significantly. Our results suggest that zinc ions have a positive inotropic effect on isolated diaphragm muscle. The increase in PT may be explained by a zinc-activated Ca2+ uptake by sarcoplasmic reticulum. This was followed by an increase in the rate of rise of tension development, which was secondary to increased -dP/dt. The mechanism(s) by which extracellular Ca2+ contributes to this action of zinc is not known.

The effect of zinc ions on the activity of metallo-beta-lactamases of Bacteroides fragilis.

The zinc supplement required to achieve the maximum activity of metallo-beta-lactamases from 12 Bacteroides fragilis isolates was investigated. Changes in absorbance of imipenem in a spectrophotometric assay with crude cell extracts were performed in the presence and absence of various concentrations of zinc sulphate. The greatest degree of imipenem hydrolysis was seen with the addition of between 50 and 500 microM zinc sulphate, and the degree of stimulation of enzyme activity in the strains tested varied six-fold. Increasing the zinc sulphate concentration resulted in inhibition of hydrolysis with extracts of low enzymic activity. These findings indicate the importance of determining the optimal zinc concentration for each strain tested in kinetic studies of metallo-beta-lactamases.

Influence of Zn2+ on the kinetic events that contribute to the 500-kDa dextran-sulfate-dependent activation of factor XII (Hageman factor).

The effect of zinc ions on kinetic and equilibrium steps that may contribute to the activation and subsequent autoactivation of human blood coagulation factor XII in the presence of 500-kDa dextran sulfate was studied. To analyze the results, the expression of the overall autoactivation constant that had been established from the model presented in a previous study was used. Comparison of the kinetics obtained at different levels of zinc, which included amounts lower than the residual concentration introduced by NaCl in the incubation mixture, suggested that the addition of Zn2+ up to 5 microM lowered the mean number of sites available for the binding of factor XII to the surface from 220 to 172 and increased the rate of the first-order activation of factor XII by one order of magnitude, from (1.6 +/- 0.4) x 10(-4) s(-1) to (8.0 +/- 0.4) x 10(-4) s(-1) in the presence of 550 nM dextran sulfate. Neither the factor XII/surface dissociation constant (1 microM), the apparent catalytic constant, nor the apparent Michaelis-Menten constant associated with the postulated multi-stage kinetic sequence were affected by the presence of zinc. Most experimental trends induced by the presence of zinc could be successfully interpreted by using the model, thus reinforcing its reliability under different conditions.

ニッケルめっき膜の残留応力に及ぼす亜鉛イオンの影響

ニッケルめっき膜の残留応力に及ぼす亜鉛イオンの影響

Intracellular Zinc Movement and Its Effect on the Carbohydrate Metabolism of Isolated Rat Hepatocytes

The effect of zinc ions on carbohydrate metabolism and intracellular Zn2+ was studied in hepatocytes from fed rats. The addition of ZnCl2 to the medium led to an almost 3-fold increase in lactate production and an increase in net glucose production of about 50%. Half-maximal rates occurred at about 40 microM ZnCl2. These effects were not seen with Mn2+, Co2+, or Ni2+ up to 80 microM, whereas Cu2+ at 80 microM and Cd2+ or Pb2+ at 8 microM exhibited similar effects as 80 microM ZnCl2. Changes in intracellular Zn2+ were followed by single cell epifluorescence using zinquin as a specific probe. Intracellular free Zn2+ in isolated hepatocytes was 1.26 +/- 0.27 microM, and the addition of ZnCl2 led to a concentration-dependent increase in epifluorescence. CdCl2 or PbCl2 at 8 microM was as potent as ZnCl2 at 20-80 microM, whereas NiCl2 at 80 microM was without effect. ZnCl2 completely abolished the inhibition of glycolysis by glucagon (cAMP). Glucagon led to a pronounced drop in cytosolic Zn2+. Both glucagon and zinc stimulated glycogenolysis by increasing the phosphorylation of glycogen phosphorylase but acted oppositely on glycolysis. Zinc overcame the inactivation of pyruvate kinase by glucagon without changing the hormone-induced protein phosphorylation. The antagonistic action of zinc and cAMP on glycolysis together with the rapid and marked decrease in free zinc concentration induced by glucagon (cAMP) may indicate an as yet unknown role of zinc as an important mediator of regulation of carbohydrate metabolism.

The effect of zinc ions on the platinum electrode in alkaline solutions

Concentrated KOH + K 2Zn(OH) 4 + H 2O and KOH + H 2O electrolytes were investigated by cyclic voltammetry and hydrogen-electrode rest potential measurements. The adsorption of zincate ions on the platinum electrode is demonstrated by modifications of the voltammograms and shifts in rest potentials. Interference with the hydrogen reactions in the voltammograms by zincate ions prevents the use of the H 2/Pt reference electrode for rest potential measurements in zincate-containing solutions.

Surface-independent acceleration of factor XII activation by zinc ions. I. Kinetic characterization of the metal ion rate enhancement

The effect of zinc ions (Zn(II)) on the activation of factor XII in the absence of a procoagulant surface was investigated by initial velocity kinetic studies at I = 0.15, pH 7.4, and 25 degrees C. Zinc ions at concentrations greater than 160 microM potentiated 99-fold the kcat/KM for the activation of factor XII by kallikrein and, at an optimum concentration of 110 microM, accelerated 140-fold the apparent kcat/KM for factor XII autoactivation. High molecular weight kininogen had no effect on either metal-potentiated reaction. Analysis of the factor XII concentration dependence of initial activation rates revealed that Zn(II), at levels that saturate the effect, accelerates kallikrein activation of factor XII by lowering KM (from 52 to 7.3 microM) and raising kcat (from 2.6 to 31 min-1). For the autocatalytic activation reaction of factor XII in the presence of optimal Zn(II), apparent KM and kcat values of 2.4 microM and 0.041 min-1, respectively, were determined, but these parameters were not resolvable in the absence of the metal ion. Zinc ions minimally affected kallikrein enzymatic activity and inhibited factor XIIa enzymatic activity with KI values of 20-40 microM, suggesting that the rate-enhancing effects of the metal ion are due to interactions with the substrate (factor XII) rather than with the enzyme. The Zn(II) inhibition of factor XIIa enzymatic activity accounted for a decreased Zn(II) enhancement of factor XII autoactivation at high metal ion concentrations (> 110 microM). The Zn(II) concentration dependence of the acceleration of factor XII activation reactions were sigmoid and characterized by Hill coefficients of 3.3-4.3, suggesting that cooperative binding of at least four zinc ions to factor XII was responsible for the Zn(II) potentiating effect. The Zn(II) enhancement of the rates of factor XII activation decreased both above and below pH 7.4 with midpoint pH values of 6.5-7.0 and 8.0, consistent with histidine and possibly water ligands mediating Zn(II) binding to the protein. Despite an apparent weaker binding of Zn(II) to factor XII at pH 6.5, indistinguishable maximum accelerating effects of the metal ion were observed at saturation at this pH, indicating that the increased positive charge of factor XII resulting from protonation at the lower pH did not mimic the effect of Zn(II) binding. These results imply that zinc ions induce a conformational change in factor XII that makes it a better substrate for its enzyme activators.

Insulinlike effects of zinc ion in vitro and in vivo. Preferential effects on desensitized adipocytes and induction of normoglycemia in streptozocin-induced rats

Insulinlike effects of zinc ion in vitro and in vivo. Preferential effects on desensitized adipocytes and induction of normoglycemia in streptozocin-induced rats

Effect of zinc ions on the biochemical behavior of simian virus 40 small-t antigen expressed in bacteria.

The simian virus 40 small-t antigen contains 10 cysteine residues, 6 of which are organized in two CysXCysXXCys clusters. Mutation of individual Cys residues in the two clusters or mutation of specific residues found between these clusters causes pronounced instability of the protein in animal cells. Protein instability correlates with failure of the bacterially expressed mutant proteins to bind zinc ions, an interaction which allows purification of large amounts of small-t antigen in monomeric form.

Effect of zinc ion on the interaction of some amino acid compounds of copper(II) with hydrogen peroxide

Reaction of elemental copper and zinc powder mixtures with glycine (NH 2·CH 2COOH; HA) or aspartic acid (NH 2CHCOOHCH 2COOH; H 2B) (in 1:1:2 ratio, respectively) in the presence of excess hydrogen peroxide (H 2O 2) at 50°C, results in the formation of a new mixed metal peroxy carbonate compound corresponding to formula [Cu(Zn) 2(O 2 2−) (CO 3) 2(H 2O) 4], while the same reaction with elemental copper powder alone yields merely peroxy amino acid compounds having the formula [Cu(O 2 2−) (HA) 2(H 2O)] and [Cu(O 2 2−) (H 2B) (H 2O) 2] for glycine and aspartic acid, respectively. These compounds have been characterized by elemental analysis, ESR, and electronic and IR spectra. It is interesting to note that both amino acids are converted to carbonate in the presence of zinc alone. A method analogous to that described above, for the reaction of elemental copper, zinc powder mixtures with succinic acid [(CH 2COOH) 2] or acetic acid (CH 3COOH) in excess H 2O 2, on the other hand, gave a product essentially comprising copper succinate or acetate, respectively. These observations suggest an interesting and perhaps important phenomenon by which only the simple amino acids such as glycine and aspartic acid are converted to carbonates while their corresponding carboxylic acids form only their respective salts.

Cytotoxicity of zinc in vitro

The effect of zinc ions on B16 mouse melanoma lines, HeLa cells and I-221 epithelial cells was investigated in vitro in order to ascertain whether sensitivity to Zn 2+ is a general feature of cells in vitro and in an attempt to elucidate the mechanism(s) of zinc cytotoxicity. The proliferation of B16, HeLa and I-221 cell lines was inhibited by 1.25 × 10 −4, 1.50 × 10 −4 and 1.50 × 10 −4 mol/l Zn 2+, respectively. The free radical scavengers, methimazole and ethanol, did not suppress the toxicity of Zn 2+, neither did superoxide dismutase or catalase. The addition of the chelating agent EDTA reduced the zinc cytotoxicity. It was possible to suppress the cytotoxicity of zinc by increasing the concentration of either Fe 2+ or Ca 2+ but not Mg 2+, which suggests that a prerequisite for the toxic action of zinc is entry into cells using channels that are shared with iron or calcium. This view was supported by experiments in which transferrin intensified the cytotoxic action of zinc in serum-free medium. Another agent facilitating zinc transport, prostaglandin E 2, inhibited the proliferation of the B16 melanoma cell line. There were no conspicuous differences in zinc toxicity to pigmented and unpigmented cells. The toxic effect of zinc in the cell systems studied exceeded that of iron, copper, manganese and cobalt in the same concentration range. In vitro, Zn 2+ should be regarded as a dangerous cation.

Effect of zinc ions on tRNA structure: imino proton NMR spectroscopy.

The structure of tRNA in solution was explored by NMR spectroscopy to evaluate the effect of divalent cations, especially zinc, which has a profound effect on the chromatographic behaviour of tRNAs in certain systems. The divalent ions Mg2+ and Zn2+ have specific effects on the imino proton region of the 1H NMR spectrum of valine transfer RNA (tRNA(Val] of Escherichia coli and of phenylalanine transfer RNA (tRNA(Phe] of yeast. The dependence of the imino proton spectra of the two tRNAs was examined as a function of Zn2+ concentration. In both tRNAs the tertiary base pair (G-15).(C-48) was markedly affected by Zn2+ (shifted downfield possibly by as much as 0.4 ppm); this is the terminal base pair in the augmented dihydrouridine helix (D-helix). Base pair (U-8).(A-14) in yeast tRNA(Phe) or (s4U-8).(A-14) in tRNA1(Val), which are stacked on (G-15).(C-48), was not affected by Zn2+, except when 1-2 Mg2+ ions per tRNA were also present. Another imino proton that may be affected by Zn2+ in both tRNAs is that of the tertiary base pair (G-19).(C-46). The assignment of this resonance in yeast tRNA(Phe) is tentative since it is located in the region of highly overlapping resonances between 12.6 and 12.3 ppm. This base pair helps to anchor the D-loop to the T psi C loop.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies with an automated kinetic assay for plasma angiotensin-converting enzyme activity and its potentiation by zinc ion

Measurement of plasma angiotensin-converting enzyme (ACE) is of value in sarcoidosis and, when specific inhibitors are prescribed therapeutically, in hypertension and heart failure. In this study a rapid kinetic assay for estimation of plasma ACE is described and assessed. In particular the effects of zinc ion have been studied. In contrast to previous reports, a marked potentiation of ACE activity by micromolar concentrations of zinc was noted. The relationship between plasma zinc concentration and ACE activity in vivo was also investigated and related to albumin concentration. The findings may have implications for interpretation of plasma ACE activity in patients with low plasma zinc levels.

Effect of zinc ions on tRNA structure : I. Reversed-phase chromatography

The effect of zinc on the chromatographic behavior of four tRNAs was examined on RPC-5 and Aminex A-28 columns. RPC-5 contains dichlorodifluoroethylene beads coated with a quaternary ammonium compound where the substituents are: R 1 = methyl, and R 2-4& z.dbnd; C 8-10 hydrocarbons. Aminex A-28 contains quaternary ammonium covalently attached to styrene-divinylbenzene copolymer lattice and R 1-3 are methyl groups. The retentions of tRNA Val, tRNA Ile, and tRNA Lys of E. coli and yeast tRNA Phe on RPC-5 were all markedly increased by Zn 2+ ions. In contrast, no increased retention due to Zn 2+ was observed when tRNA Phe was chromatographed on Aminex A-28. A model for chromatography on RPC-5 is developed which treats the elution behavior of tRNAs from this matrix as the sum of ionexchange and hydrophobic interactions. The chromatography of tRNA in the presence and absence of Zn 2+ is interpreted in terms of this model and the effects of sodium chloride concentration, temperature, and pH were explored as the experimental variables. These experiments suggest that in the absence of Zn 2+ tRNA does not interact appreciably with the hydrophobic surface of the column. The addition of Zn 2+ has three effects on chromatography: (1) a decrease in the number of anionic sites on the tRNA which interact with the positively charged ammonium ion, (2) an increase in affinity of the tRNA for these ionic sites, and (3) an increase in affinity of tRNA for hydrophobic sites on the column. All three effects were fully reversed by the addition of Cd 2+ (10 m M) or Mg 2+ (35 m M), but only partially reversed at lower concentrations of these competing ions. These results show that chromatography on RCP-5 can be a sensitive physical chemical technique for examination of the structure of tRNA, and probably for other nucleic acids as well.

The effect of zinc ions on the thrombin-binding capacity of fibrin

The effect of zinc ions on the thrombin-binding capacity of fibrin

Angiotensin I-converting enzyme inhibitor derived from an enzymatic hydrolysate of casein. Part III. Effects of zinc ion on inhibition by angiotensin I-converting enzyme inhibitor derived from casein.

Angiotensin I-converting enzyme inhibitor derived from an enzymatic hydrolysate of casein. Part III. Effects of zinc ion on inhibition by angiotensin I-converting enzyme inhibitor derived from casein.

Enhancement of DNA binding and mutagenicity of 1-nitropyrene by zinc acetate in Salmonella typhimurium TA100.

The effect of zinc acetate on the mutagenicity of 1-nitropyrene (1-NP) in Salmonella typhimurium TA100 was examined. By the pre-treatment of the cells with zinc ions (0.24 mM) the revertant colonies caused by 1.5 microM of 1-NP in the pre-incubation mixtures increased approximately 3-fold, while the survival colonies decreased to approximately 75% under the same conditions. The enhancing effect of zinc ions on the mutagenicity was not dependent on the increase of 1-NP incorporation into the cells. The addition of zinc ions to whole cell preparations had no enhancing effect on the 1-NP reductase activity. The effect of zinc acetate on the binding of [3H]1-NP to DNA in S. typhimurium TA100 was examined. The amount of [3H]1-NP bound to DNA increased by the pre-treatment of the cells with zinc ions. A good correlation was found between the extent of binding of 1-NP to DNA and the frequency of induced histidine reversions in the cells treated with zinc ions under the experimental conditions used.

The effect of zinc ion on adenylate cyclase in rat testicular tissue.

The effect of zinc ion on adenylate cyclase in rat testicular tissue.

Effect of zinc ion on human chorionic gonadotropin-stimulated in vitro production of cyclic AMP and testosterone by rat testis.

This study explores the effects of several divalent metal ions on the in vitro production of cyclic AMP, cyclic GMP, and testosterone by rat testicular tissue and on the amount of binding of [125I]human chorionic gonadotropin (hCG) in the testis. Zn2+ at concentrations of 10(-6) to 10(-4) M enhanced the hCG-stimulated production of cyclic AMP and testosterone, but only in the presence of Ca2+ X [125I]hCG binding to rat testicular tissue was not affected by Zn2+ X Cu2+, Ni2+, Co2+, and Mn2+ did not increase cyclic AMP or testosterone production in concentrations of 10(-7) to 10(-3) M and even inhibited them at a high concentration (10(-2) M). Cyclic GMP production was not affected by these divalent ions. These results suggest that Zn2+ may play an important role in rat testicular steroidogenesis.

Ab initio molecular orbital study on the effects of zinc ion, its ligands and ionic amino acid residues for proton transfer energetics between glu 270 and Zn co-ordinated water molecule in carboxypeptidase A

Thezinc-water-Glu 270 system was reported from the X-ray crystallographic study of native carboxypeptidase A(CPA) (Lipscomb et al., 1968). General base catalysis by the γ-carboxylate of Glu 270 was proposed for peptidase activity of CPA. The effects of zinc ion and its ligands (Glu 72, His 69-Asp 142, His 196) for proton transfer between Glu 270 and Zn co-ordinated water molecule in CPA were studied by the ab initio SCFLCAO-MO method. The results show that the proton transfer from the Zn co-ordinated water molecule to the γ-carboxylate of Glu 270 is greatly promoted by the Zn ion and, conversely, is greatly inhibited by its ligands. The facilitation effect of Zn ion and the inhibition effect of its ligands for the proton transfer were analysed by using the energy decomposition analysis. Moreover, calculations including all side chains of ionic amino acid residues and main chain residues in CPA as point fractional charges were performed. The results show that the proton transfer is affected by the ionic amino acid residues and is not affected by the main chain residues.