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Biomedical subjects

G Bartosz

Publications and source records attributed to G Bartosz.

At least 55 records · Page 3Linked to original sources
PubMed1997

Antioxidant and prooxidant properties of captopril and enalapril.

Captopril ([2S]-1-[3-mercapto-2-methyl-propionyl]-L-proline) was found to protect erythrocytes from hemolysis caused by 2,2'-azobis (2-amidinopropane) (AAPH) and hypochlorite, erythrocyte membranes from lipid peroxidation caused by tert-butyl hydroperoxide (tBOOH) and hypochlorite, erythrocyte membrane ATPases from inactivation caused by tBOOH and hemoglobin from oxidation caused by AAPH and tBOOH. In all these systems enalapril ([S]-1-[N-(1-[ethoxycarbonyl]-3-phenylpropyl)-L-alanyl]-L-proline) was not protective or even increased the damage, especially with hypochlorite, probably due to chloramine formation. Captopril but not enalapril inhibited ascorbate autoxidation caused by Cu2+, which indicates that captopril binds Cu2+. On the other hand, deoxyribose degradation caused by iron and copper ions and DNA damage by o-phenanthroline/Cu2+/H2O2/beta-mercaptoethanol was enhanced by both captopril and enalapril. The effect of captopril was usually higher, apparently due to the reducing properties of captopril, which could reduce metal ions enabling their participation in the Fenton reaction. These results indicate that only -SH-group-containing inhibitors of angiotensin-converting enzyme (ACE) may exhibit antioxidant properties, and that the antioxidant/prooxidant action of ACE inhibitors depends on the system studied in vitro.

Adenosine Triphosphatases↗
PubMed1997

Decrease in accessible thiols as an index of oxidative damage to membrane proteins.

The effect of several oxidative agents (hydrogen peroxide, tert-butyl hydroperoxide, menadione, AAPH, peroxynitrite and ionizing radiation) on the ratio of weakly to strongly immobilized residues of erythrocyte membrane-bound maleimide-tempo spin label (h(w)/h(s) ratio) was studied in order to test the hypothesis that a decrease in the h(w)/h(s) ratio may be a general index of oxidative damage to membrane proteins. Most of the agents studied decreased though H2O2 almost did not affect and ionizing radiation increased the h(w)/h(s) ratio. In parallel, the ratio of DTNB accessible/DTNB inaccessible membrane protein-SH groups was determined from membrane-SH group measurements with the Ellman reagent in the absence and in the presence of sodium dodecyl sulfate. This ratio decreased in all cases studied and seems to be a more universal and easy to measure parameter to describe the oxidative damage to membrane proteins.

Adult↗
PubMed1997

Estimation of oxidative stress in Saccharomyces cerevisae with fluorescent probes.

Oxidation of dichlorofluorescin and dihydrofluorescin and transport of their oxidation products were studied in Saccharomyces cerevisiae cells given diacetates of these compounds. It was found that addition of peroxidase significantly accelerates the formation of dichlorofluorescein and fluorescein, indicating that peroxidase activity may be a limiting factor in studies of cellular oxidation using these probes. A significant leakage of dichlorofluorescin and dihydrofluorescin, and of their oxidized forms from the yeast cells, was found, without any apparent lag period. This phenomenon complicates interpretation of data obtained with the fluorescent precursors used but, on the other hand, points to the possibility of using measurements of dichlorofluorescein or fluorescein in the extracellular medium for studies of cellular oxidation processes.

Biological Transport↗
PubMed1997

Effect of postirradiation treatment on the radiation-induced haemolysis of human erythrocytes.

The effect of postirradiation conditions on the haemolysis of y-irradiated (2.1 kGy) human erythrocytes was studied. Haemolysis was inhibited by incubation in mannitol and sucrose instead of saline, by hypertonicity of the medium and by calcium chelators. Dithiothreitol, butylated hydroxytoluene, deferoxamine, DIDS (in inhibitor of anion exchange) and furosemide (an inhibitor of K/Cl and K/Na/Cl cotransport) did not slow down the haemolysis. Apparently, the radiation-induced haemolysis is due to the formation of membrane pores leaky for electrolytes. From the inhibition of haemolysis by mannitol, apparent pore radius was estimated to be about 0.7 nm. The pores appear to be transient, the average pore number per cell being much less than unity.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1997

Transport of glutathione S-conjugates in Escherichia coli.

There are no reports concerning glutathione-S-conjugates transport in prokaryotic cells, although many studies have been performed in eukaryotic systems. This study demonstrates that glutathione S-conjugates (2,4-dinitrophenyl-S-glutathione and bimane-S-glutathione) are transported also out of Escherichia coli K12 cells. This transport is inhibited by vanadate, fluoride and other inhibitors of glutathione S-conjugate transport in mammalian cells suggesting a similarity of this process to that known in eukaryotes.

Biological Transport, Active↗
PubMed1997

Penetration of erythrocyte membrane by peroxynitrite: participation of the anion exchange protein.

Participation of the anion exchange protein (Band 3 protein) of the erythrocyte membrane in the transport of peroxynitrite into erythrocytes was shown by partial inhibition of hemoglobin oxidation by extracellular peroxynitrite in cells treated with Band 3 inhibitors. These results demonstrate that permeation in the anionic form may be a minor pathway in the membrane transport of the peroxynitrite anion/peroxynitrous acid couple, especially in membranes reach in anion exchangers or channels.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1996

An electron spin resonance assay of glutathione S-conjugate transport.

A method for studying export of glutathione S-conjugates from cells is proposed based on the use of the spin label tempo-maleimide. This compound is conjugated intracellularly with glutathione and the concentration of the exported conjugate is measured in cell supernatants in an electron spin resonance spectrometer after reoxidation with ferricyanide. This method allows for measurements of micromolar concentrations of the conjugate and requires low amounts of cells.

Adult↗
PubMed1996

Effect of peroxynitrite on erythrocytes.

The action of peroxynitrite on human erythrocytes and erythrocyte membranes was studied. Peroxynitrite (0.1-2 mM) induced a transient decrease of intracellular reduced glutathione, oxidized membrane protein -SH groups, initiated membrane lipid peroxidation and inactivated erythrocyte membrane acetylcholinesterase and ATPase activities. Membranes exposed to peroxynitrite showed aggregation and nitration of proteins and changes in protein organization detectable with a maleimide spin label.

Acetylcholinesterase↗
PubMed1996

Transport of glutathione S-conjugates in the yeasts Saccharomyces cerevisiae.

Transport of 2,4-dinitrophenyl-S-glutathione (DNP-SG) and a fluorescent glutathione S-conjugate, bimane-S-glutathione (B-SG) was studied in the baker's yeasts (S. cerevisiae). Both conjugates were exported from the cells; the transport was inhibited by fluoride and vanadate like in mammalian cells. B-SG was also found to be accumulated in the vacuoles. The transport rate of DNP-SG outside the cell was higher in a vacuolar-deficient strain. A significant ATP-dependent uptake of (3H)-DNP-SG by vacuoles was found. These results indicate that S. cerevisiae transport glutathione S-conjugates both outside the cells and into the vacuoles.

Biological Transport↗
PubMed1996

Effect of amino acid peroxides on the erythrocyte.

The effect of amino acid peroxides, relatively stable products of irradiation of amino acid solutions, on erythrocyte components was studied. Interaction of proline, lysine, valine, and leucine peroxides (100-300 mu M) with erythrocyte membranes brought about a decrease of membrane protein -SH group content and of activities of (Na+, K+)-ATPase and Ca2+ -ATPase, and induced aggregation of membrane proteins, due mainly to the formation of interpeptide disulfides. Interaction of amino acid peroxides with hemoglobin brought about hemoglobin oxidation to methemoglobin. The effects of amino acid peroxides are similar to those of t-butyl hydroperoxide. These results indicate that peroxides of amino acid and proteins, which can also be formed under physiological conditions, may be mediators of the cellular action of reactive oxygen species.

Amino Acids↗
PubMed1996

The copper complex of captopril is not a superoxide dismutase mimic. Artefacts in DMPO spin trapping.

The effect of captopril and of its copper complex on several superoxide-dependent reactions used to detect and assay superoxide dismutase activity was studied, including pyrogallol and hematoxylin autoxidation and Nitro Blue Tetrazolium reduction. In none of these systems were superoxide dismutase-like properties of captopril/Cu apparent. Captopril/Cu decreased the yield of DMPO-OH adducts generated by KO2 but this effect may be due to the acceleration of the decay of the adduct by captopril/Cu.

Antioxidants↗
PubMed1996

Lack of evidence of oxidative damage in antioxidant-deficient strains of Saccharomyces cerevisiae.

The content of reactive carbonyls and of glutathione-protein mixed disulfides, two indices of oxidative stress, were compared in wild-type Saccharomyces cerevisiae and in strains deficient in superoxide dismutase and catalase, and of decreased glutathione level. Both indices were higher in stationary than in logarithmic cultures and were not increased in antioxidant-deficient strains. Oxidation of dichlorofluorescin, an estimate of peroxide production, measured in the presence of exogenous peroxidase, was higher in antioxidant-deficient strains. These results corroborate our previous results on compensatory antioxidant mechanisms in the mutant yeast strains.

Acatalasia↗
PubMed1996

Peroxynitrite: mediator of the toxic action of nitric oxide.

Peroxynitrite (oxoperoxonitrate(-1)), anion of peroxynitrous acid, is thought to mediate the toxic action of nitric oxide and superoxide anion. Peroxynitrite is formed in a fast reaction between these species, reacts with all classes of biomolecules, is cytotoxic, and is thought to be involved in many pathological phenomena. Its main reactions involve one- and two-electron oxidation and nitration. Protein nitration is often used as a footprint of peroxynitrite reactions in vivo. Nitration of tyrosine and of tyrosyl residues in proteins may be an important mechanism of derangement of biochemical signal transduction by this compound. However, apparently beneficial effects of peroxynitrite have also been described, among them formation of nitric oxide and nitric oxide donors in reactions of peroxynitrite with thiols and alcohols.

Animals↗
PubMed1996

Glutathione depletion in the yeast Saccharomyces cerevisiae.

The effect of chosen compounds on the total glutathione (GSH) level in stationary cultures of S. cerevisiae was compared. 1-Chloro-2,4-dinitrobenzene, 1-fluoro-2,4-dinitrobenzene, maleimide, iodacetamide and allyl alcohol (1 mM), and menadione (0.5 mM) caused an almost complete GSH depletion during several minutes. Bromobenzoic acid and chloramine T (I mM), and daunomycin (60 mu M) induced a slower GSH decrease, down to 30-70% after 60 min. Paraquat (1 mM), CuSO(4) (0.5 mM) and cadmium acetate (1 mM) decreased glutathione level down to ca 70%. Diamide (0.5 mM), phenazine methosulphate, phenylhydrazine, acetylphenylhydrazine and H(2)O(2) (1 mM), and t-butyl hydroperoxide (2 mM) did not affect total GSH during 60-min exposure. There was no clear-cut dependence between the ability of various chemicals to deplete cellular GSH and their increased toxicity to a glutathione-poor mutant.

Alkylating Agents↗
PubMed1995

Transport of bimane-S-glutathione in human erythrocytes.

Export of glutathione S-conjugate of bimane (BSG) was studied in human erythrocytes. Characteristics of the BSG transport is similar to that of dinitrophenyl-S-glutathione (DNP-SG). BSG transport has two kinetic components, one of high affinity and low capacity (Km = 7.4 +/- 0.2 mumol/ml cells, Vm = 2.7 +/- 0.1 nmol/min per ml RBC) and another of low affinity and high capacity (Km = 242 +/- 8 mumol/ml cells, Vm = 9.6 +/- 1.6 nmol/min per ml RBC). BSG export is inhibited by vanadate (Ki = 65 +/- 6 microM) and fluoride (Ki = 11.4 +/- 0.8 mM). Activation energy of the transport is 67 +/- 7 kJ/mol. BSG transport is independent of membrane potential; its rate increases with pH in the pH range of 6-8, in line with the assumption that the anionic conjugate is cotransported with proton. BSG import to erythrocyte membrane inside-out vesicles is stimulated by ATP. Fluorimetric measurements of BSG export require low amounts of cells and may also be useful for other cell types as an alternative to studies of glutatione S-conjugate transport using radioactive substrates.

Biological Transport↗
PubMed1995

Effect of inhibitors on the transport of dinitrophenyl-S-glutathione in human erythrocytes.

Effect of inhibitors on and pH dependence of the export of dinitrophenyl-S-glutathione (DNP-SG), a glutathione S-conjugate formed upon in vivo conjugation of 1-chloro-2,4-dinitrobenzene to glutathione, was studied in intact human erythrocytes. The transport was inhibited by orthovanadate (IC50 = 80 microM) and fluoride (IC50 = 9 nM). Erythrocyte anion exchange (Band 3) protein inhibitors DIDS and SITS did not exert any significant effect on the transport. The transport rate increased with increasing extracellular pH in the range of 6.0-8.0. The Arrhenius activation energy of the process was 72.4 +/- 1.3 kJ/mol. Membrane potential, extracellular sodium/potassium concentration ratio and extracellular osmolality in the range 300-600 mOsm did not influence the export rate.

Biological Transport↗