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Results for “Sulfhydryl Compounds”

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At least 19 recordsLinked to original sources

PubMed1992

Homocysteine and other sulfhydryl compounds enhance the binding of lipoprotein(a) to fibrin: a potential biochemical link between thrombosis, atherogenesis, and sulfhydryl compound metabolism.

We have previously shown that lipoprotein(a) [Lp(a)], an atherogenic lipoprotein that contains apolipoprotein(a), which shares partial structural homology to plasminogen, binds to a plasmin-modified fibrin surface, and we have postulated that this interaction may be atherogenic. Moderate elevations in blood homocysteine, a relatively common condition, predispose to premature atherosclerosis. The reasons for this are not established. We now report that homocysteine, at concentrations as low as 8 microM, significantly increases the affinity of Lp(a) for fibrin. Homocysteine induces a 20-fold increase in the affinity between Lp(a) and plasmin-treated fibrin and a 4-fold increase with unmodified fibrin. Lp(a) binding is inhibited by epsilon-aminocaproic acid, indicating lysine binding site specificity. Homocysteine does not enhance the binding of Lp(a) to other surface-bound proteins. Cysteine, glutathione, and N-acetylcysteine also increase the affinity between Lp(a) and fibrin. Homocysteine does not affect the binding of low density lipoprotein or plasminogen to fibrin, nor does it alter the gel-filtration elution pattern of Lp(a). Immunoblot analysis documents the fact that homocysteine partially reduces Lp(a). These results suggest that homocysteine alters the intact Lp(a) particle so as to increase the reactivity of the plasminogen-like apolipoprotein(a) portion of the molecule. The observation that sulfhydryl amino acids increase Lp(a) binding to fibrin suggests a biochemical relationship between sulfhydryl compound metabolism, thrombosis, and atherogenesis.

Blotting, Western↗

PubMed1991

The inhibition of metabolic oxalate production by sulfhydryl compounds.

A number of sulfhydryl compounds were shown to inhibit CO2 and oxalate formation from glyoxylate by rat liver homogenates and hepatocytes. The most significant inhibition occurred with cysteine and this inhibition was concentration-dependent. In rats made hyperoxaluric by administering ethylene glycol in their drinking water, daily intraperitoneal injections of cysteine caused a rapid and marked decrease in urinary oxalate excretion which was maintained over the duration of the treatment (28 days). Over this time period, the level of urinary oxalate excretion in these ethylene glycol-treated rats was reduced to that of the controls. It is postulated that the decrease is due to the formation of a cysteine-glyoxylate adduct, 2-carboxy-4-thiazolidine carboxylate, which prevents glyoxylate being further oxidized to oxalate. Cysteine or similar sulphydryl compounds may therefore have potential as therapeutic agents in the prevention of renal stones.

Aluminum↗

PubMed1987

False-positive results for ketone with the drug mesna and other free-sulfhydryl compounds.

All free-sulfhydryl compounds tested produced false-positive reactions in the Legal test for ketones. The color developed in the ketone pad of urine dipsticks [N-Multistix SG, Multistix 10 SG (Ames), and Chemstrip 9 (Boehringer-Mannheim)] was misinterpreted for ketone bodies, both by visual and automated reading. In contrast to the reaction with true ketones, a drop of glacial acetic acid added onto the ketone pad of dipsticks discharged the false-positive red color. A red-violet also developed instantly with free -SH compounds in the Acetest tablet assay (Ames), but quickly faded. In general, the presence of acidic groups such as -COOH and -SO3H in the structure appeared to increase the nitroprusside reactivity of free -SH compounds, whereas the presence of a -NH2 group appeared to decrease it. Currently, false-positive ketone reactions ascribable to a free -SH group are most likely to be seen for urine containing mesna. The false-positive test for ketones caused by free -SH compounds can be recognized and ruled out by proper procedures. On the other hand, this chromogenic reaction with free thiols might be used for monitoring urinary excretion of mesna.

False Positive Reactions↗

PubMed1988

Modulation of myoglobin-H2O2-mediated peroxidation reactions by sulfhydryl compounds.

The ability of specific low molecular weight sulfhydryl compounds to inhibit the myoglobin-H2O2 peroxidation of uric acid and arachidonic acid was investigated. alpha-Mercaptopropionyl glycine, N-acetylcysteine, and reduced glutathione inhibited both the oxymyoglobin and metmyoglobin H2O2-mediated peroxidation of uric acid in a dose-dependent manner. The IC50 for each drug ranged between 20 to 100 microM and was dependent on the presence of a reduced sulfhydryl group since neither oxidized glutathione nor methionine effectively blocked uric acid peroxidation. Similar inhibition of oxymyoglobin and metmyoglobin H2O2-mediated peroxidation of arachidonic acid was also observed with alpha-mercaptopropionyl glycine, reduced glutathione, and cysteine. Under conditions of this assay, the ferrous form of myoglobin and H2O2 produced approximately three times the amount of formaldehyde from dimethylsulfoxide than ferric myoglobin (metmyoglobin) and H2O2. However, metmyoglobin and H2O2 were more effective than either oxymyoglobin and deoxymyoglobin in mediating arachidonic acid peroxidation. Further, neither mannitol nor benzoic acid (known scavengers of .OH) effectively blocked myoglobin H2O2-induced peroxidation of either uric acid or arachidonic acid. Visible absorption spectra of oxymyoglobin and metmyoglobin after incubation with H2O2 indicates the formation of a relatively stable ferriperoxide derivative of myoglobin. The formation of the ferriperoxide myoglobin derivative was partially inhibited by the addition of reduced sulfhydryl compounds. These data are consistent with the hypothesis that during reperfusion injury of the ischemic myocardium, the phagocytic cell or intracellular-derived H2O2 may react with myoglobin and initiate peroxidation reactions independent of .OH formation leading to cell injury. The cardioprotective effects of alpha-mercaptopropionyl glycine and other sulfhydryl-containing compounds during reperfusion injury may be attributed, at least in part, to their ability to inhibit myoglobin-H2O2-mediated peroxidation reactions.

Arachidonic Acids↗

PubMed1991

Factors influencing the in vitro growth of Mycobacterium leprae: effect of sulfhydryl compounds.

In an attempt to determine the factors that influence the in vitro growth of Mycobacterium leprae in DH medium, the effects of sulfhydryl compounds were studied. Growth of M. leprae was monitored using two biochemical indicators. Only the sulfhydryl compounds, in reduced form, containing carboxyl group could support the growth of M. leprae. Higher cell yields were obtained when these sulfhydryl compounds were supplemented with dithiothreitol, presumable to keep the monothiols in reduced state during long incubation periods. Ascorbic acid could not replace dithiothreitol for this purpose. It is suggested that these carboxylated sulfhydryl compounds play a role in the metabolic activity of M. leprae along with maintaining low redox potential of the medium.

Adenosine Triphosphate↗

PubMed1991

Regional variations in total and nonprotein sulfhydryl compounds in the human gastric mucosa and effects of ethanol.

This study evaluated the regional distribution of sulfhydryl compounds in the human gastric mucosa and the effect of ethanol on gastric sulfhydryl tissue levels. Total sulfhydryl, glutathione, and cysteine and their oxidized forms were measured in biopsy specimens taken from the gastric body and antrum of 22 healthy volunteers. Total sulfhydryl and glutathione contents of the body of the stomach were significantly higher than those of the antrum. In contrast, cysteine concentration was higher in the gastric antrum than in the body. No difference was found in the levels of oxidized sulfhydryls between the gastric body and antrum. The effect of acute administration of ethanol on gastric sulfhydryl content was studied in nine subjects. Ethanol caused gross mucosal damage and lowered the concentration of sulfhydryl compounds in both the body and the antrum. In 10 chronic alcoholics total sulfhydryl and glutathione, but not cysteine, were markedly decreased in the gastric body but not in the antrum as compared with nonalcoholic controls. In conclusion, 1) the human gastric body contains significantly higher tissue levels of total sulfhydryls and glutathione and lower concentrations of cysteine than the antrum; 2) ethanol in a damaging concentration significantly decreases gastric tissue levels of sulfhydryl compounds; and 3) chronic ethanol intake lowers total sulfhydryl and glutathione tissue levels in the gastric body.

Adult↗

PubMed1989

Involvement of cellular sulfhydryl compounds in the inhibition of RNA synthesis by selenite.

Selenite has been shown previously to inhibit cellular RNA synthesis. Based upon our previous observation that selenite inhibits purified RNA polymerase only in the presence of a sulfhydryl compound (Frenkel et al., Mol Pharmacol 31: 112-116, 1987), we hypothesized that the inhibition of cellular RNA synthesis by selenite involves endogenous sulfhydryl compounds. We found that depletion of cells of endogenous sulfhydryl compounds, by exposure to diethylmaleate (DEM), virtually eliminated the inhibitory effect of a 1-hr exposure of cells to selenite. This inhibition was restored to normal or higher levels when the selenite was reacted with glutathione or cysteamine prior to addition to the DEM-treated cells. RNA synthesis in DEM-treated cells was inhibited after a 4-hr exposure to higher concentrations of selenite. In contrast to the effect of DEM, specific depletion of the cells of glutathione, by exposure to buthionine sulfoximine, had no effect on the inhibition of RNA synthesis by selenite. These results demonstrate the involvement of endogenous cellular sulfhydryl compounds in the inhibition of RNA synthesis by selenite, but indicate that glutathione, in particular, is not involved in this inhibition.

HeLa Cells↗

PubMed1979

Thermosensitization by sulfhydryl compounds of exponentially growing Chinese hamster cells.

The effect of various sulfhydryl compounds on the survival of exponentially growing monolayer cultures of Chinese hamster cells (HA1) heated to temperatures of 37-43 degrees was examined. Concentrations of cysteamine which were nontoxic or minimally toxic at room temperature or 37 degrees became increasingly toxic at elevated temperatures, greatly potentiating the killing produced by heat alone in the absence of cysteamine. This enhancement of hyperthermia-induced cell killing increased with increasing cysteamine concentration, increasing duration of cysteamine exposure, and increasing temperature. Studies with synchronized Chinese hamster cells heated at 43 degrees for 1 hr in the presence of 16 mM cysteamine demonstrated that the potentiation of heat killing occurred in all phases of the cell cycle. Similarly, enhancement of hyperthermia-induced cell killing was seen for asynchronous cells exposed to 2-amino-ethylisothiourium bromides and cysteine, but the magnitude of the effect differed for the various sulfhydryl compounds.

Animals↗

PubMed1988

Evidence for the involvement of sulfhydryl compounds in the inhibition of cellular DNA synthesis by selenite.

Previous studies have demonstrated that selenite inhibits cellular DNA synthesis. We have now found that endogenous cellular sulfhydryl compounds are involved in this effect of selenite. Treatment of cells with diethylmaleate, which produces a nonspecific depletion of cellular sulfhydryl compounds, resulted in a significant decrease in the sensitivity of DNA synthesis to inhibition by selenite. This decrease was eliminated by exogenous cysteine, but not by cystine. Similarly, DNA synthesis in nuclei isolated from diethylmaleate-treated cells was much less sensitive to inhibition by selenite than was synthesis in nuclei isolated from control cells. In contrast, treatment with buthionine sulfoximine, which specifically depletes the cells of glutathione, had no effect on the inhibition of DNA synthesis by selenite, indicating that cellular glutathione is not involved in the inhibition. Nevertheless, glutathione is able to compensate to some extent for the decreased level of sulfhydryl compounds in nuclei isolated from DEM-treated cells (although not as well as cysteine). Thus, although glutathione is able to potentiate the inhibition of cellular DNA synthesis by selenite, it apparently does not function in this capacity in the cell.

Buthionine Sulfoximine↗

PubMed1987

Inhibition of RNA and DNA polymerases by the product of the reaction of selenite with sulfhydryl compounds.

Sodium selenite has previously been shown to inhibit DNA and RNA synthesis in both intact cells and isolated nuclei. Nevertheless, DNA and RNA polymerases, the enzymes responsible for this synthesis, are insensitive to inhibition by selenite. Several DNA and RNA polymerases have now been shown to be inhibited by selenite in the presence of sulfhydryl compounds. This inhibition is due to the reaction of selenite with the sulfhydryl compounds to form selenotrisulfide derivatives which inhibit the enzymes. The selenotrisulfides decrease the Vmax of the polymerase reaction and increase the apparent Km for the triphosphates, but do not alter the apparent Km of the enzyme for the DNA template. There are differences in potency between selenotrisulfides formed from similar sulfhydryl compounds such as mercaptoethanol and mercaptoethylamine. There are also differences in the sensitivity of different polymerases to inhibition by the selenotrisulfides.

Chemical Phenomena↗

PubMed1985

The reaction between organic nitrates and sulfhydryl compounds. A possible model system for the activation of organic nitrates.

The rate of loss of the sulfhydryl group, determined with the Ellman reagent, was used to derive second order rate constants for the reaction of a series of organic nitrates with a series of sulfhydryl compounds. For the organic nitrates, increases in the rate of reaction with cysteine, in general, ran parallel both with increases in pharmacological potency (flow in the Langendorff heart) and with increases in total clearance. Cysteine was the most active sulfhydryl compound examined, which is compatible with a possible role as an important nitrate receptor. Under some conditions the rate of loss of the sulfhydryl group was much greater than the rate of formation of nitrite ion. This indicates the presence of a reaction intermediate, probably a thionitrate. It is suggested that, in vivo, a thionitrate could function as an important intermediate in the activation of guanylate cyclase.

Animals↗

PubMed1987

The changes in sulfhydryl compounds in plasma, liver and brain after acute and chronic ethanol administration in rats.

The content of sulfhydryl compounds in proteins and non-proteins of plasma, liver and brain after acute and chronic ethanol administration was investigated in rats. After ethanol ingestion for 4 weeks (6 g/kg, day 30% w/v) significant changes were observed in plasma proteins and in liver proteins and non-proteins. In brain proteins and non-proteins we did not find any changes in sulfhydryl compounds content after acute and chronic ethanol administration.

Alanine Transaminase↗

PubMed1991

Sulfhydryl compounds inhibit the cyto- and geno-toxicity of o-phenylphenol metabolites in CHO-K1 cells.

The effects of cysteine and reduced glutathione (GSH) on the genotoxicity of o-phenylphenol (OPP) and its metabolites, phenylhydroquinone (PHQ) and phenylbenzoquinone (PBQ), were examined using the frequency of sister-chromatid exchanges (SCEs) and chromosome aberrations in CHO-K1 cells as parameters. Cytotoxic (cell-progression delay) and cytogenetic effects induced by a 3-h treatment with OPP, PHQ (100 micrograms/ml) or PBQ (50 micrograms/ml) with S9 mix after a 27-h expression time were inhibited by cysteine or GSH (3-10 mM). Materials corresponding to the cysteine or GSH adducts were found by HPLC in each incubation mixture. In the culture without S9 mix, PHQ and PBQ showed severe cytotoxicity since no metaphases could be obtained at doses over 25 and 5 micrograms/ml, respectively, and the sulfhydryl compounds inhibited the toxicity by the formation of adducts with PBQ and by inhibiting the formation of PBQ in the case of PHQ. With PHQ, the sulfhydryl compounds appeared to inhibit autooxidation. However, the sulfhydryl compounds did not inhibit the cytotoxic and cytogenetic effects caused by OPP in the cell mixture without S9 mix, but on the contrary intensified them. No adduct formation was detected in the incubation solution. On the basis of these results, it is considered that electrophilic quinone (PBQ) and/or semiquinone (phenylsemiquinone, PSQ) radicals, capable of binding to nucleophilic small molecules (such as cysteine and GSH) or (biological) macromolecules, are produced from metabolite PHQ in metabolic oxidation of OPP, and induce cyto- and geno-toxic effects in the cells. The cyto- and geno-toxic effects of OPP itself to the cells are clearly independent of any electrophilic radical reaction.

Animals↗

PubMed1988

The role of sulfhydryl compounds in mammalian melanogenesis: the effect of cysteine and glutathione upon tyrosinase and the intermediates of the pathway.

The effect of cysteine and glutathione on mammalian melanogenesis has been studied. It has been shown that their action is mediated by two different mechanisms. (a) The reaction of the thiol groups with dopaquinone after the tyrosinase-catalyzed oxidation of tyrosine and dopa. This mechanism leads to the formation of sulfhydryl-dopa conjugates and finally sulfur-containing pigments, phaeomelanins instead of eumelanins. This fact might produce an inhibition of melanogenesis due to the slower rate of chemical reactions involved in the polymerization of such thiol-conjugates when compared to that of indoles. (b) The direct interaction between the sulfhydryl compounds and the tyrosinase active site. This interaction may regulate the activity of the enzyme. It is shown that Harding-Passey mouse melanoma tyrosinase is more sensitive to sulfhydryl compounds than mushroom tyrosinase. Cysteine always produces an inhibition of the tyrosinase hydroxylase and dopa oxidase activities of melanoma tyrosinase, this inhibition becoming greater as the cysteine concentration increases. On the other hand, glutathione produces an activation of the tyrosine hydroxylase activity below 3 mM and an inhibition at higher concentrations. The limit between the enzymatic activation and inhibition appears at glutathione concentrations similar to the physiological levels of this compound found in melanocytes. Although the switch from eumelanogenesis to phaeomelanogenesis occurs at much lower concentrations of glutathione, taking into account these data it is discussed that this sulfhydryl compound may regulate not only the type but also the amount of melanin formed inside melanocytes.

Animals↗

PubMed1978

Effect of vitamins, antioxidants and sulfhydryl compounds on in vitro rat brain lipid peroxidation.

The effect of retinol, retinylacetate, alpha-tocopherol, alpha-tocopherylacetate, synthetic antioxidants (DPPD, BHT, DAH, and Ethoxyquine) sulfhydryl compounds (reduced glutathione and cysteine) on rat brain lipid peroxidation has been studied using the TBA method. Retinol and retinyl acetate inhibit brain lipid peroxidation, alpha-tocopherol is less effective than vitamin A, while alpha-tocopherol acetate has no antioxidant property. Ascorbic acid stimulates the peroxidation, at pH 5.0. The synthetic antioxidants are all potent inhibitors of brain lipid peroxidation, DPPD being the most effective, while the sulfhydryl compounds at a concentration of 1 x 10(-3)M has a slight potentiating effect.

Animals↗

PubMed1984

Modification of ultraviolet radiation effects on the membrane of myelinated nerve fibers by sulfhydryl compounds.

The modification of the ultraviolet blocking of sodium channels and of the ultraviolet-induced potential shift of the gating parameters by means of the sulfhydryl compounds l-cysteine and 2-mercaptoethanol was investigated in the node of Ranvier under voltage-clamp conditions. The UV wavelength was 280 nm. The radiation-induced potential shift of the voltage-dependent gating parameters was prevented or even reversed by the action of the sulfhydryl compounds (internal application), while the blocking effect was not affected. It is concluded that the two radiation effects are caused by two separate photoreactions. Internally applied N-ethylmaleimide, binding specifically to protein-SH groups, exhibits an effect similar to the ultraviolet-induced potential shift, without affecting the maximum sodium permeability. Therefore, the ultraviolet-induced potential shift might be caused by a photocatalyzed oxidation of -SH groups of membrane proteins changing the surface charge density at the inner side of the nodal membrane.

Animals↗

PubMed1976

Sulfhydryl compounds in melanocytes of yellow (Ay/a), nonagouti (a/a), and agouti (A/A) mice.

CLEFFMANN (1953, 1963a,b) has reported that yellow but not black melanocytes of agouti (A/A) rabbits contained reducing sulfhydryl compounds. We have attempted to repeat CLEFFMANN's observations in mouse melanocytes of the lethal yellow (Ay/a), nonagouti (a/a) and agouti (A/A) genotypes. Our results contradict those of CLEFFMANN and reveal that yellow and black melanocytes, regardless of genotype, possess equivalent amounts of histochemically detectable sulfhydryl compounds. These results do not support the hypothesis that agouti-locus genes act by controlling the sulfhydryl metabolism of pigment cells.

Animals↗

PubMed1985

Nonprotein sulfhydryl compounds in canine gastric mucosa: effects of PGE2 and ethanol.

By use of an in vivo canine chambered stomach preparation in which the gastric mucosa was partitioned into two equal halves, the effect of topical 16,16-dimethyl PGE2 (DMPGE2) (1 microgram/ml of perfusate) and 8% and 40% ethanol on tissue levels of nonprotein sulfhydryl compounds was assessed. Both DMPGE2 and 8% ethanol significantly increased (P less than 0.005) mucosal levels of nonprotein sulfhydryls when compared with corresponding mucosa bathed with saline alone. In contrast, mucosa bathed with 40% ethanol showed significantly decreased levels. If mucosa was bathed with DMPGE2 or 8% ethanol prior to exposing the stomach to 40% ethanol, this depletion in sulfhydryl compounds was not observed. Since other experimental observations have shown that exogenously administered prostaglandins and mild irritants (such as low-dose alcohol) can prevent gastric mucosal damage by necrotizing agents (such as high-dose alcohol), our findings are consistent with the hypothesis that nonprotein sulfhydryls may play a role in mediating gastric mucosal protection.

16,16-Dimethylprostaglandin E2↗