SEARCH · PubMed Health

Results for “THIOSULFATES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources

PubMed1977

Selective reactivity of rhodanese sulfhydryl groups with 5,5'-dithio-bis(2-nitrobenzoic acid).

The reactivity of the sulfhydryl groups of sulfur-containing and sulfur-free rhodanese (thiosulfate : cyanide sulfurtransferase, EC 2.8.1.1) with 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB) has been investigated. Only 0.6 sulfhydryl group of the sulfur-containing enzyme reacts with DTNB. After removal of sulfur from persulfide groups a further 0.6 sulfhydryl group (i.e. a total of 1.2) becomes accessible to the reagent. The resulting enzyme-thionitrobenzoate complex shows an absorption spectrum with a shoulder at 325 nm due to bound thionitrobenzoate. Both thiosulfate and cyanide remove thionitrobenzoate from the enzyme restoring its catalytic properties. The modified enzyme is protected from alkylation by iodoacetate until thionitrobenzoate is removed. The existence of a further sulfhydryl group close to the catalytic one is suggested.

Animals↗

PubMed1977

Studies of the N-bromosuccinimide inactivation of the enzyme rhodanese.

The enzyme rhodanese (Thiosulfate: cyanide sulphurtransferase, EC 2.8.1.1) is rapidly inactivated by treatment with N-bromosuccinimide. Spectrophotometric titration and sodium dodecyl sulfate polyacrylamide gel electrophoresis show that neither tryptophan oxidation nor polypeptide chain cleavage can account for the inactivation. Sulfhydryl group assays using the colormetric reagent 5,5'-dithiobis(2-nitrobenzoic acid) after destruction of excess N-bromosuccinmide, indicate that approximately 2 sulfhydryl groups per enzyme molecule are lost. Further, rhodanese inactivated by N-bromosuccinimide can be reactivated (approximately 95%) by incubation with the substrate thiosulfate. It is postulated that N-bromosuccinimide inactivates rhodanese by inducing the formation of a disulfide bond involving the active site sulfhydryl group of the enzyme and a second sulfhydryl group which can be brought close to the active site in the flexible native structure.

Binding Sites↗

PubMed2000

Characterization of a sulfurtransferase from Arabidopsis thaliana.

A database search for similarities between sequenced parts of the Arabidopsis thaliana genome with known sulfurtransferase sequences from Escherichia coli and mammals was undertaken to obtain information about plant sulfurtransferase-like proteins. One gene and several homologous EST clones were identified. One of the EST clones was used for screening an Arabidopsis cDNA library. The isolated full-length clone consists of 1134 bp and encodes a 42.6 kDa protein that includes a putative transit peptide sequence of about 7.1 kDa. Sequence comparisons with known sulfurtransferases from different organisms confirmed high homology between them and the existence of several highly conserved regions. Results of a Southern blot performed with genomic Arabidopsis DNA showed the occurrence of at least two sulfurtransferase-like isozymes in Arabidopsis. Recombinant proteins with and without the putative transit peptide were expressed in E. coli with an N-terminal His6-tag, purified by affinity chromatography and tested for enzyme activity using different sulfur donors and acceptors. Both recombinant proteins catalyzed the formation of SCN- from thiosulfate and cyanide as a rhodanese per definition; however, both recombinant proteins preferred 3-mercaptopyruvate to thiosulfate. A monospecific antibody produced by using the mature recombinant protein as an antigen recognized a single protein band in total extracts of Arabidopsis plants equating to the full-length protein size. A single band equating to the size of the mature protein was detected from purified Arabidopsis mitochondria, but there was no antigenic reaction with any protein from chloroplasts. The function of the protein is still speculative. Now tools are available to elucidate the roles and substrates of this sulfurtransferase in higher plants.

Amino Acid Sequence↗

PubMed1993

Properties of Azotobacter vinelandii rhodanese.

Rhodanese (thiosulfate: cyanide sulfurtransferase, E.C. 2.8.1.1) was purified from the nitrogen fixing organism Azotobacter vinelandii, and its amino acid composition was determined. The enzyme is a single polypeptide chain of M(r) 29,000 which showed an apparent pI of 4.7 and no presence of isoenzymes. Steady-state initial velocity measurements indicate that the enzyme catalyzes the transfer of sulfane sulfur of thiosulfate either to cyanide or to dihydrolipoate by way of a double displacement mechanism.

Amino Acids↗

PubMedDate not supplied

In vitro and in vivo comparison of sulfur donors as antidotes to acute cyanide intoxication.

Antidotes for cyanide (CN) intoxication include the use of sulfane sulfur donors (SSDs), such as thiosulfate, which increase the conversion of CN to thiocyanate by the enzyme rhodanese. To develop pretreatments that might be useful against CN, SSDs with greater lipophilicity than thiosulfate were synthesized and assessed. The ability of SSDs to protect mice against 2LD50 of sodium cyanide (NaCN) administered either 15 or 60 min following administration of an SSD was assessed. To study the mechanism of action of the SSD, the candidate compounds were examined in vitro for their effect on rhodanese and 3-mercaptopyruvate sulfurtransferase (MST) activity under increasing SSD concentrations. Tests were conducted on nine candidate SSDs: ICD1021 (3-hydroxypyridin-2-yl N-[(N-methyl-3-aminopropyl)]-2-aminoethyl disulfide dihydrochloride), ICD1022, (3-hydroxypyridin-2-yl N-[(N-methyl-3-aminopropyl)]-2-aminoethyl disulfide trihydrochloride), ICD1584 (diethyl tetrasulfide), ICD1585 (diallyl tetrasulfide), ICD1587 (diisopropyl tetrasulfide); ICD1738 (N-(3-aminopropyl)-2-aminoethyl 2-oxopropyl disulfide dihydrochloride), ICD1816 (3,3'-tetrathiobis-N-acctyl-L-alanine), ICD2214 (2-aminoethyl 4-methoxyphenyl disulfide hydrochloride) and ICD2467 (bis(4-methoxyphenyl) disulfide). These tests demonstrated that altering the chemical substituent of the longer chain sulfide modified the ability of the candidate SSD to protect against CN toxicity. At least two of the SSDs at selected doses provided 100% protection against 2LD50 of NaCN, normally an LD99. All compounds were evaluated using locomotor activity as a measure of potential adverse behavioral effects. Positive hypoactivity relationships were found with several disulfides but none was found with ICD1584, a tetrasulfide. Separate studies suggest that the chemical reaction of potassium cyanide (KCN) and cystine forms the toxic metabolite 2-iminothiazolidine-4-carboxylic acid. An alternative detoxification pathway, one not primarily involving the sulfur transferases. may be important in pretreatment for CN intoxication. Although studies to elucidate the precise mechanisms are needed. it is clear that these newly synthesized compounds provide a new rationale for anti-CN drugs, with fewer side-effects than the methemoglobin formers.

Animals↗

PubMed2000

In vitro effects of anionic sulfur compounds on the spectrophotometric properties of native DNA.

Several anionic sulfur compounds are recognized as efficacious pretreatments for sulfur mustard (HD) poisoning. Our intent was to see if pretreatment compounds had a direct effect on DNA, a site where HD damage is thought to occur. A modification of the method of Szinicz et al. (Arzneim.-Forsch. 1981; 31: 1,713-1,717) was used to analyze the UV/VIS spectrum (205-400 nm) (n = 6) of calf thymus DNA (10-15 x 10(3) kDa) in the absence or presence of increasing concentrations of sodium thiosulfate, sodium 2-aminoethanethiosulfonate (thiotaurine), sodium metabisulfite or sodium sulfate. All compounds produced concentration-dependent absorbance decreases primarily at 212 nm, but also at 259 nm, with the exception of sodium sulfate. For example, 8.36 x 10(-4) M sodium thiosulfate reduced the absorbance of DNA at 212 nm by >60%. The kinetics of sulfur compounds on native DNA need further study. We propose that these anionic sulfur compounds interact with DNA possibly by changing the topology of this macromolecule. Effects may be due to interactions of these sulfur compounds at higher concentrations with DNA, with resulting ligand-DNA supercoiling. This process could protect against HD intoxication, which is caused in part by the uncoiling of DNA.

Animals↗

PubMed1999

Extended heme promiscuity in the cyanobacterial cytochrome c oxidase: characterization of native complexes containing hemes A, O, and D, respectively.

The cyanobacteria Anacystis nidulans (Synechococcus sp. PCC6301), Synechocystis sp. PCC6803, Anabaena sp. PCC 7120, and Nostoc sp. PCC8009 were grown photoautotrophically under reduced oxygen tension in a medium with sulfate replaced by thiosulfate and nitrate replaced by ammonium as the S- and N-sources, respectively. In addition, Anabaena and Nostoc were grown under dinitrogen-fixing conditions in a medium free of combined nitrogen. Membranes were isolated from late-logarithmic cells (culture density corresponding to approximately 3 microliters packed cells per milliliter); cytoplasmic and thylakoid membranes were separated and purified according to established procedures. Acid-labile hemes were extracted from the membranes and subjected to reversed-phase high-performance liquid chromatography. Separated hemes were analyzed spectroscopically and identified by comparison with authentic standards. In addition to hemes B, A, and O, the latter of which was induced under semianaerobic conditions only, substitution of thiosulfate and ammonium for the oxy-anions sulfate and nitrate led to the appearance of spectrally discernible heme D in the membranes and extracts therefrom. However, spectroscopic and kinetic investigation of the membrane-bound heme D rather disproved any reaction with oxygen or carbon monoxide. Kinetic measurements performed with the membrane-bound respiratory oxidase gave evidence for only two kinetically competent terminal oxidases, a3 and o3, both apparently associated with a single type of apoprotein, viz. subunit I of the known cyanobacterial aa3-type cytochrome c oxidase. The heme D, on the other hand, seems to form a spectrally distinguished, yet kinetically ill-defined hemoprotein complex which does not qualify as a fully functional d-type terminal oxidase on our (wild-type) cyanobacteria even after growth under semianaerobic pseudo-reducing conditions. Also growth (of Anabaena and Nostoc) under dinitrogen-fixing conditions did not change this situation. Thus, we are left with (wild-type) cyanobacteria forming an unbranched respiratory chain with only a single type of terminal oxidase protein, viz. the known aa3-type cytochrome c oxidase. This oxidase, however, may incorporate different prosthetic (heme) groups in the sense of "heme promiscuity." Biosynthesis of the different heme groups thereby seems to respond to the ambient redox environment. In particular, however, conditions for expression of the two quinol oxidases potentially and additionally coded for by the genome of, e. g., Synechocystis sp. PCC6803 (see http://www.kazusa.or.jp/cyano), have not yet been found.

Acids↗

PubMed1980

Active sulfate reabsorption in the proximal convolution of the rat kidney: specificity, Na+ and HCO3- dependence.

Using the standing droplet technique in the proximal convolution and simultaneous microperfusion of the peritubular capillaries, the decrease in luminal sulfate concentration with time and the zero net flux transtubular concentration difference of sulfate (delta CSO42-) at 45 s was determined - the latter being taken as a measure of the rate of active sulfate reabsorption. Starting with 0.5 mmol/l sulfate in both perfusates the delta CSO42- value of 0.35 mmol/l was approached exponentially with a half value time of 4.3 s. The delta CSO42- values in the early proximal and late proximal convolution did not deviate from each other. If the Na+ concentration in the perfusates was reduced, the delta CSO42- approached zero and extrapolated to a slightly negative value (Ci greater than Co). When 1 mmol/l ouabain was added to the perfusates delta CSO42- decreased by 66% (the latter experiments were performed in the golden hamster which is more sensitive to ouabain than the rat). 1 mmol/l thiosulfate diminished delta CSO42- by 68% and 1 mmol/l molybdate by 24%. Omitting or replacing bicarbonate by HEPES or glycodiazine reduced the sulfate reabsorption significantly, while acetazolamide (0.1 mmol/l) and increasing the CO2-pressure from 4.66 to 14.0 kPa (i.e. 5-15% CO2) had no effect. SITS 1 mmol/l had no effect on sulfate reabsorption. The data indicate that the sulfate reabsorption is driven by a Na+ gradient and inhibited by thiosulfate and molybdate, i.e. molecules which have a similar tetrahedral molecule structure. The sulfate reabsorption depends in an undefined manner on the presence of bicarbonate ions.

Absorption↗

PubMed1988

Antiarthritic synergism of combined oral and parenteral chrysotherapy. II. Increased inhibition of activated leukocyte oxygen burst by combined gold action.

We have observed an antiarthritic effect of combined chrysotherapy in adjuvant arthritis. Since superoxide radicals (O2-) are potent mediators of rheumatoid inflammation, we studied the combined effect of auranofin (AF) and injectable golds on luminol-dependent chemiluminescence (LDCL) and O2- generation by cytochrome-c reduction of activated leukocytes by different receptor-mediated stimuli: phorbol myristic acetate, 10(-6) M; f-Met-Leu-Phe, 10(-6) M; and poly-L-histidine, 10(-5) M. AF, 0.6 and 0.9 micrograms Au/ml, inhibited 34 and 58% of O2- generation, respectively; the addition to AF of 0.3 micrograms Au/ml of gold thiosulfate (GTS) increased this inhibition to 84 and 97% of the oxygen burst. Similar synergistic potentiation inhibition was obtained by LDCL. When the inhibition of O2- generation by the combined action of AF and GTS was compared with AF + gold sodium thiomalate (GTM), only GTS showed an activation on AF's inhibition of the oxygen burst of human leukocytes. The ligand thiosulfate in equimolar concentrations to GTS had a statistically significant (P less than 0.01) inhibitory effect on AF's blockade of O2- generation during the first 5 min of the interaction with the PMNs; thiomalate had no effect. Sequential pretreatment of PMNs with AF and GTS on O2- generation revealed that for synergism of combined gold action to take place, the cell membrane had to be subjected first to the action of oral gold or to the simultaneous combined action of oral and parenteral gold.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1990

Primary structure of avian hepatic rhodanese.

Rhodanese (thiosulfate: cyanide sulfurtransferase, EC 2.8.1.1.) was purified from chicken livers and its amino acid sequence was determined. The enzyme has a specific activity of 676 IU and a molecular weight of 32,255. The primary structure of 289 amino acids was solved by sequential Edman degradation of overlapping peptides obtained by selected enzymatic and chemical cleavages. The amino terminus was blocked, and the carboxy-terminus was heterogeneous. Comparison of the primary structure with bovine liver rhodanese showed 212 identically matched amino acids, and the majority of amino acid differences were conservative substitutions. Reaction of the enzyme with a 1.4-fold molar excess of [2-14C]iodoacetate led to inactivation of the enzyme and carboxymethylation of Cys-244; this modification was blocked by the substrate thiosulfate.

Amino Acid Sequence↗

PubMed2001

Analysis of a 2,4,6-trichlorophenol-dehalogenating enrichment culture and isolation of the dehalogenating member Desulfitobacterium frappieri strain TCP-A.

An anaerobic, 2,4,6-trichlorophenol ortho-dehalogenating mixed culture was enriched from sediment of the river Saale (Germany). Two isolated dechlorinating colonies (MK1 and MK2) consisted of rods of different lengths and thicknesses, indicating heterogeneity. Following subcultivation with thiosulfate as alternative electron acceptor and cocultivation with Clostridium celerecrescensT, the 2,4,6-trichlorophenol-dehalogenating bacterium Desulfitobacterium frappieri strain TCP-A was isolated and characterized regarding its taxonomic properties and the spectrum of chlorophenols that it dehalogenated. Four other bacterial strains were coenriched and identified as organisms with closest phylogenetic relatedness to the Clostridium type strains C. indolis, C. glycolicum, C. hydroxybenzoicum and C. sporosphaeroides (16S rDNA sequence identities of 99.5, 99.2, 94.4, and 93.5%, respectively). Amplified ribosomal DNA restriction analysis of the original dehalogenating cultures MK1 and MK2 (when not exposed to thiosulfate) confirmed the microbial heterogeneity and revealed the presence of two additional species related to the type strains of C. celerecrescens and Clostridium propionicum. Only one copy of the 16S rRNA genes of Desulfitobacterium frappieri in each of the clone libraries of MK1 and MK2 (containing 136 and 56 clones, respectively) was found by dot-blot hybridization, suggesting a relatively low number of the dehalogenating bacterium within the enrichment culture.

Anaerobiosis↗

PubMedDate not supplied

Selective enrichment and characterization of Roseospirillum parvum, gen. nov. and sp. nov., a new purple nonsulfur bacterium with unusual light absorption properties.

A new type of phototrophic purple bacterium, strain 930I, was isolated from a microbial mat covering intertidal sandy sediments of Great Sippewissett Salt Marsh (Woods Hole, Mass., USA). The bacterium could only be enriched at a wavelength of 932 (+/- 10) nm. Cells were vibrioid- to spirilloid-shaped and motile by means of bipolar monotrichous flagellation. The intracytoplasmic membranes were of the lamellar type. Photosynthetic pigments comprised bacteriochlorophyll a and the carotenoids spirilloxanthin and lycopenal. The isolated strain exhibited an unusual, long-wavelength absorption maximum at 911 nm. Sulfide or thiosulfate served as electron donor for anoxygenic phototrophic growth. During growth on sulfide, elemental sulfur globules formed outside the cells. Elemental sulfur could not be further oxidized to sulfate. In the presence of sulfide plus bicarbonate, fructose, acetate, propionate, butyrate, valerate, 2-oxoglutarate, pyruvate, lactate, malate, succinate, fumarate, malonate, casamino acids, yeast extract, L(+)-alanine, and L(+)-glutamate were assimilated. Sulfide, thiosulfate, or elemental sulfur served as a reduced sulfur source for photosynthetic growth. Maximum growth rates were obtained at pH 7.9, 30 degrees C, 50 micromol quanta m-2 s-1 of daylight fluorescent tubes, and a salinity of 1-2% NaCl. The strain grew microaerophilically in the dark at a partial pressure of 1 kPa O2. The DNA base composition was 71.2 mol% G + C. Sequence comparison of 16S rRNA genes indicated that the isolate is a member of the alpha-Proteobacteria and is most closely related to Rhodobium orientis at a similarity level of 93.5%. Because of the large phylogenetic distance to known phototrophic species of the alpha-Proteobacteria and of its unique absorption spectrum, strain 930I is described as a new genus and species, Roseospirillum parvum gen. nov. and sp. nov.

Bacteria↗

PubMed2000

Evaluation of antidotes for extravasation injury produced by 6-hydroxymethylacylfulvene (MGI 114), a novel cytotoxic antitumor agent, in an intradermal toxicity model in rats.

MGI 114 (HMAF, 6-hydroxymethylacylfulvene) is a cytotoxic drug currently in phase II human clinical trials. As with other anticancer agents, inadvertent drug extravasation may result in perivascular irritation and/or necrosis. In this study the degree of soft tissue injury produced by MGI 114 after intradermal administration to rats was quantified and four potential antidotes for extravasation injuries caused by MGI 114 were evaluated. Intradermal injections of MGI 114 (0.2 ml, concentrations 0.1, 0.5 or 1.0 mg/ml) and a positive control, doxorubicin (0.2 ml, concentration 2 mg/ml) were administered to male Fischer 344 rats in an experiment designed to establish a model for antidote evaluation. Dermal lesions at the injection sites were measured and quantitated as the total area under the lesion area-time curve (AUC). Physiological saline, sodium thiosulfate, dimethylsulfoxide (DMSO) and local cooling, were then compared as potential antidotes in this model. In the initial study, dermal lesions (erythema, ulcerations and eschar formation) occurred at the MGI 114- and doxorubicin-treated sites. The lesion area resulting from MGI 114 was dose-related and was greatest at approximately 5 days, with resolution by day 7-22. Doxorubicin-induced lesions were comparable in area to those induced by the highest dose of MGI 114, but persisted approximately twice as long. In the antidote study, sodium thiosulfate administration resulted in approximately 20% diminution of lesion area and AUC value when compared to untreated controls. Normal saline caused slight reductions in maximum lesion area, but had little effect on AUC values. Local cooling also caused a modest reduction in the maximum lesion area, but actually resulted in higher AUC values by prolonging eschar duration. DMSO provided near complete tissue protection from intradermal exposure to MGI 114. In this model MGI 114 and doxorubicin were found to produce similar soft tissue injuries, but MGI 114-induced lesions tended to show a more rapid resolution. Topical DMSO treatment was found to produce the most effective protection against MGI 114-induced local tissue irritation and necrosis.

Administration, Cutaneous↗

PubMed2004

Thialkalivibrio halophilus sp. nov., a novel obligately chemolithoautotrophic, facultatively alkaliphilic, and extremely salt-tolerant, sulfur-oxidizing bacterium from a hypersaline alkaline lake.

A new chemolithoautotrophic, facultatively alkaliphilic, extremely salt-tolerant, sulfur-oxidizing bacterium was isolated from an alkaline hypersaline lake in the Altai Steppe (Siberia, Russia). According to 16S rDNA analysis and DNA-DNA hybridization, strain HL 17T was identified as a new species of the genus Thialkalivibrio belonging to the gamma subdivision of the Proteobacteria for which the name Thialkalivibrio halophilus is proposed. Strain HL 17T is an extremely salt-tolerant bacterium growing at sodium concentrations between 0.2 and 5 M, with an optimum of 2 M Na+. It grew at high concentrations of NaCl and of Na2CO3/NaHCO3 (soda). Strain HL 17T is a facultative alkaliphile growing at pH range 7.5-9.8, with a broad optimum between pH 8.0 and 9.0. It used reduced inorganic sulfur compounds (thiosulfate, sulfide, polysulfide, elemental sulfur, and tetrathionate) as energy sources and electron donors. In continuous culture under energy limitation, thiosulfate was stoichiometrically oxidized to sulfate. In sodium carbonate medium under alkaline conditions, the maximum growth rate was similar, while the biomass yield was lower as compared with the NaCl-grown culture. The maximum sulfur-oxidizing capacity measured in washed cells was higher in the soda buffer independent of the growth conditions. The compatible solute content of the biomass was higher in the sodium chloride-grown culture than in the sodium carbonate/bicarbonate-grown culture. The data suggest that the osmotic pressure differences between soda and NaCl solutions might be responsible for the difference observed in compatible solutes production. This may have important implications in overall energetic metabolism of high salt adaptation.

Chromatiaceae↗

PubMed2004

Gestational urinary hyperthiosulfaturia protects hypercalciuric normal pregnant women from nephrolithiasis.

Urinary calcium excretion increases by 1-2-fold during gestation in normal, uncomplicated pregnant women. Hypercalciuria occurs in all trimesters and elevates urine supersaturation with regards to calcium oxalate. However, crystalluria has not been a frequent clinical finding and stone formation is not a common complication of pregnancy. To elucidate this discrepancy we measured various chemical entities (i.e. calcium, oxalate, uric acid, phosphorous, magnesium, citrate, sulfate and thiosulfate) in urine at the end of each trimester of 25 pregnant women. Twenty-five healthy women served as controls. Our observations show that endogenous thiosulfate, a natural component of urine, increased considerably during pregnancy to approximately 36, 38 and 40 microM/24 hour at the end of each three trimesters. One month after delivery, endogenous thiosulfaturia and hypercalciuria, in parallel, returned to initial normal values. Consequently, it seems that gestational hyperthiosulfaturia protects hypercalciuric normal pregnant women from the risk of nephrolithiasis.

Adult↗

PubMed1979

Transfer of persulfide sulfur from thiocystine to rhodanese.

THiocystine (bis-[2-amino-2-carboxyethyl]trisulfide) is a natural substrate for rhodanese (thiosulfate:cyanide sulfurtransferase, EC 2.8.1.1). Analogs of thiocystine were prepared by eliminating the carboxyl or amino group or by lengthening the carbon chain. Of these only homothiocystine (bis-[2-amino-2-carboxypropyl]trisulfide) had appreciable activity as a substrate. At pH 8.6, the optimum for rhodanese, transfer of sulfane sulfur to cyanide in the presence of rhodanese was nonspecific. Only the sulfane sulfur of 35S-labeled thiocystine was transferred to rhodanese. Thus, thiocystine and thiosulfate both produce a rhodanese persulfide as a stable intermediate in sulfur transfer.

Chemical Phenomena↗

PubMed1983

Interaction of rhodanese with intermediates of oxygen reduction.

Cyanide-promoted inactivation of the enzyme rhodanese [thiosulfate sulfurtransferase (EC 2.8.1.1)] in the presence of ketoaldehydes is caused by reduced forms of molecular oxygen generated during autoxidation of the reaction products. The requirement of both catalase and superoxide dismutase to prevent rhodanese inactivation indicates that hydroxyl radical could be the most efficient inactivating agent. Rhodanese, also in the less stable sulfur-free form, shows a different sensitivity towards oxygen activated species. While the enzyme is unaffected by superoxide radical, it is rapidly inactivated by hydrogen peroxide. The extent of inactivation depends on the molar ratio between sulfur-free enzyme and oxidizing agent. Fully inactive enzyme is reactivated by reduction with its substrate thiosulfate.

Animals↗

PubMed1983

Effect of chlorpromazine on cyanide intoxication.

Previous reports from our laboratory indicated that prophylactic protection against cyanide intoxication in mice can be enhanced by administration of chlorpromazine when it is given with sodium thiosulfate. The mechanism of potentiation of sodium thiosulfate by chlorpromazine was studied alone and in combination with sodium nitrite. Although chlorpromazine was found to induce a hypothermic response, the mechanism of enhancement of the antagonism of cyanide by chlorpromazine does not correlate with the hypothermia produced. Various other possible mechanisms were investigated, such as rate of methemoglobin formation, enzymatic activity of rhodanese and cytochrome oxidase, and alpha-adrenergic blockade. The alpha-adrenergic blocking properties of chlorpromazine may provide a basis for its antidotal effect, since this protective effect can be reversed with an alpha-agonist, methoxamine.

Animals↗