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PubMed1991

Whole blood cyanide levels of mainly dietary origin in a human population sample in Port Harcourt, Nigeria.

Whole blood cyanide levels in a human population sample of volunteers known to each gari-based meals at least once a day were determined. The most widely eaten cassava product in the area of research is gari. The mean blood cyanide obtained for healthy normal volunteers was 0.294 +/- 0.09 mumol/L while the value for sicklers was 0.398 +/- 0.008 mumol/L, indicating the possibility of reduced rate of metabolism and excretion of cyanide by sicklers as compared to non-sicklers. Investigation of post-absorption distribution indicated that whole blood cyanide increased by 0.014 mumol/L, 3-4 hours after a gari-based meal in normal volunteers. A decrease of 0.012 mumol/L occurred after a whole-rice meal. The increase in plasma cyanide 2-3 hours after a gari-based meal was about 25% more than the increase in erythrocyte cyanide suggesting a significant contribution of plasma cyanide to whole blood cyanide levels. 0.013-0.015 mg cyanide per kg of gari was determined for samples of this staple food in the locality of research.

Adolescent↗
PubMed2005

Detoxification of cyanide by woody plants.

Vascular plants possess an enzyme system that detoxifies cyanide by converting it to the amino acid asparagine. This paper examines the potential of three woody plants from the Salicaceae family to degrade cyanide. Pre-rooted trees were grown in carefully designed bioreactors with aqueous solution spiked with potassium cyanide at 23.0 +/- 1 degree C for a maximum of 144 h. Cyanide concentrations ranged from 0.95 to 1.15 CN mg/L. Cyanide in water and in plant tissues was analyzed spectrophotometrically. Results from the investigation indicated that significant reduction of aqueous cyanide was found during the presence of plants in all treatments. Little amounts of applied cyanide were detected in the tissues of plants, mainly in roots and bottom stem. Cyanide remaining in tissues varied with the species of plants, despite similar periods of exposure. The data also indicated that photolysis, hydrolysis, and microbial degradation were not occurring and that volatilization was minimal. In conclusion, transport and metabolism of cyanide in plants is most likely.

Biodegradation, Environmental↗
PubMed1977

Cyanide-resistant electron transport in sporulating Bacillus megaterium KM.

The NADH oxidase activity of stage V mother-cell membranes, isolated from sporulating Bacillus megaterium KM, shows a greater inhibition by cyanide and displays this response at lower concentrations of cyanide than the stage V forespore inner membrane. Comparison of the effects of various respiratory inhibitors reveals that the difference in cyanide sensitivity between these membranes is located on the oxidase side of the 2-heptyl-4-hydroxyquinoline N-oxide-sensitive step. Both membranes contain cytochromes a+a3, b-562, b-555, c and d, with three potential oxidases: cytochromes a+a3, o and d. Cyanide difference spectra suggest that cytochromes b-562 and d may be the components involved in the cyanide-resistant electron transport pathway. Membrane ascorbate-N,N,N',N'-tetramethylphenylenediamine and ascorbate 2,6-dichlorophenolindophenol oxidase activities are highly sensitive to cyanide. Evidence is presented for terminal branching of the respiratory chain with branches differing in cyanide sensitivity. The cyanide sensitivity of the NADH oxidase of membranes prepared from various stages of sporulation is compared. Morphogenesis of the mother-cell plasma membrane to a cyanide-sensitive form during stages II and III of sporulation is postulated.

Bacillus megaterium↗
PubMed1996

In vivo detoxification of cyanide by cystathionase gamma-lyase.

The results of several in vitro studies have suggested that the enzyme cystathionase gamma-lyase (EC 4.4.1.1) may function in the endogenous detoxification of cyanide; however, this possibility has not been investigated in vivo. If cystathionase gamma-lyase in involved in the endogenous detoxification of cyanide, it logically follows that inhibiting cystathionase gamma-lyase should increase the toxicity of cyanide. To test this hypothesis, the activity of cystathionase gamma-lyase was inhibited with a suicide inhibitor, 2-amino-4-pentynoic acid (propargyl-glycine). The activity of liver cystathionase gamma-lyase activity was decreased 96.8% by administration of propargylglycine, indicating that the propargylglycine treatment was effective. The propargylglycine treatment did not alter the activity of thiosulfate:cyanide sulfurtransferase (EC 2.8.1.1) or 3-mercaptopyruvate:cyanide sulfurtransferase (EC 2.8.1.2), two other enzymes that have been proposed to be involved in the detoxification of cyanide. The LD50 of cyanide in rats treated with propargylglycine was 5.14 +/- 0.029 mg NaCN/kg, which was significantly (P < 0.05) lower than the 5.98 +/- 0.008 mg NaCN/kg LD50 of cyanide determined in control rats. The results of these studies suggest that cystathionase gamma-lyase may participate in the detoxification of cyanide in vivo.

Animals↗
PubMed1990

Binding of thiocyanate and cyanide to manganese(III)-reconstituted horseradish peroxidase: a 15N nuclear magnetic resonance study.

Binding of thiocyanate and cyanide ions to Mn(III) protoporphyrin-apohorseradish peroxidase complex [Mn(III)HRP] was investigated by relaxation rate measurements (at 50.68 MHz) of 15N resonance of SC15N- and C15N-. At pH = 4.0 the apparent dissociation constant (KD) for thiocyanate and cyanide binding to Mn(III)HRP was deduced to be 156 and 42 mM, respectively. The pH dependence of the 15N line width as well as apparent dissociation constant for thiocyanate and cyanide binding were quantitatively analyzed on the basis of a reaction scheme in which thiocyanate and cyanide in deprotonated form bind to the enzyme in a protonated form. The binding of thiocyanate and cyanide to Mn(III)HRP was found to be facilitated by protonation of an ionizable group on the enzyme [Mn(III)HRP] with a pKa = 4.0. From competitive binding studies it was shown that iodide, thiocyanate and cyanide bind to Mn(III)HRP at the same site; however, the binding site for resorcinol is different. The apparent dissociation constant for iodide binding deduced from competitive binding studies was found to be 117 mM, which agrees very well with the iodide binding to ferric HRP. The binding of thiocyanate and cyanide was shown to be away from the metal center and the distance of the 15N of thiocyanate and cyanide from the paramagnetic manganese ion in Mn(III)HRP was found to be 6.9 and 6.6 A, respectively. Except for cyanide binding, these observations parallel with the iodide and thiocyanate ion binding to native Fe(III)HRP. Water proton relaxivity measurements showed the presence of a coordinated water molecule to Mn(III)HRP with the distance of Mn-H2O being calculated to be 2.6 A. The slow reactivity of H2O2 towards Mn(III)HRP could be attributed to the presence of water at the sixth coordination position of the manganese ion.

Binding, Competitive↗
PubMed1994

Cyanide-induced lipid peroxidation in different organs: subcellular distribution and hydroperoxide generation in neuronal cells.

To evaluate hydroperoxide generation as a potential mechanism of cyanide neurotoxicity, mice were treated with KCN (7 mg/kg, subcutaneously (s.c.)) and the level of lipid peroxidation (expressed as conjugated dienes) was measured later in various organs. Brain showed elevated conjugated diene levels after cyanide but the liver, which is not considered a target for cyanide toxicity, showed no increase. The heart also showed no increase, whereas kidney conjugated dienes slowly increased to a peak 1 h after cyanide. In vitro studies show elevation of peroxidized lipids in mouse brain cortical slices following incubation with KCN (0.1 mM). Omission of calcium from the medium or pretreatment of brain slices with diltiazem (a calcium channel blocker) prevented formation of conjugated dienes by KCN. Calcium thus appears to play a critical role in cyanide-induced generation of peroxidized lipids in neuronal cells. Subcellular fractionation of brains from mice treated with cyanide showed that lipid peroxidation increased in the microsomal fraction but not in the mitochondrial fraction. Fluorescent studies using 2,7-dichlorofluorescein (a hydroperoxide sensitive fluorescent dye) show that hydroperoxides are generated rapidly after cyanide treatment of PC12 cells, a neuron-like cell, and hydroperoxide levels remain elevated for many minutes in the presence of cyanide. These results suggest that hydroperoxide generation with subsequent peroxidation of lipids may lead to changes in structure and function of certain membranes and contribute to the neurotoxic damage produced by cyanide.

Analysis of Variance↗
PubMed1989

Cyanide, carboxyhemoglobin and blood acid-base state in animals exposed to combustion products of various combinations of acrylic fiber and gauze.

In order to examine the usefulness of blood cyanide concentrations as an indicator of whether or not a victim was alive at the start of a fire, blood cyanide concentrations were measured in the bodies that we autopsied in our institute between January 1986 and March, 1987. In the present study, bodies with advanced decomposition were excluded. Thirty-six bodies were included: cyanide as well as carboxyhemoglobin (COHb) were detected in four charred bodies found at the scene of a fire. On the other hand, cyanide was not detected in any of the remaining 30 bodies except in two cases suspected of having ingested a cyanide compound. Rats and rabbits were made to inhale the combustion products of various combinations of acrylic fiber (hydrogen cyanide generating material when heated) and gauze (carbon monoxide generating material when heated). The exposure to the combustion products was continued until death in the rat and until apnea in the rabbit. The concentration of hydrogen cyanide in the exposure chamber and that of blood cyanide, at the time the animal died, correlated with the amount of acrylic fiber heated. In addition to differences in blood COHb and cyanide concentrations, there were also differences in blood gas concentrations between the acrylic fiber and the gauze groups. When the rabbits were switched to room air after the occurrence of apnea, the blood gas value began to normalize.

Aged↗
PubMed2005

Cyanide detoxification by recombinant bacterial rhodanese.

Cyanide is a major environmental pollutant of the chemical and metallurgical industries. Although extremely toxic, cyanide can enzymatically be converted to the less toxic thiocyanate by rhodaneses (thiosulfate:cyanide sulfurtransferases, EC 2.8.1.1). We engineered a genetic system to express high levels of recombinant Pseudomonas aeruginosa rhodanese (r-RhdA) in Escherichia coli, and used this organism to test the role of r-RhdA in cyanide detoxification. Inducible expression of the rhdA gene under the control of the hybrid T7-lacO promoter yielded active r-RhdA over a 4-h period, though r-RhdA-expressing E. coli showed decreased viability starting from 1 h post-induction. At this time, Western blot analysis and enzymatic assay showed r-RhdA partition between the cytoplasm (95%) and the periplasm (5%). The accessibility of thiosulfate to r-RhdA was a limiting step for the sulfur transfer reaction in the cellular system, but cyanide conversion to thiocyanate could be increased upon permeabilization of the bacterial membrane. Specific r-RhdA activity was higher in the whole-cell assay than in the in vitro assay with pure enzyme (2154 vs. 816 micromol min-1 mg-1 r-RhdA, respectively), likely reflecting enzyme stability. The r-RhdA-dependent cyanide detoxification resulted in increased resistance of r-RhdA overexpressing E. coli to 5 mM cyanide. Bacterial survival was paralleled by release of thiocyanate into the medium. Our results indicate that cyanide detoxification by engineered E. coli cells is feasible under laboratory conditions, and suggest that microbial rhodaneses may contribute to cyanide transformation in natural environments.

Biodegradation, Environmental↗
PubMed2006

Effects of cyanide and dissolved oxygen concentration on biological Au recovery.

The number of discarded electric devices containing traces of Au is currently increasing. It is desirable to recover this Au because of its valuable physicochemical properties. Au is usually dissolved with relatively high concentrations of cyanide, which is associated with environmental risk. Chromobacterium violaceum is able to produce and detoxify small amounts of cyanide, and may thus be able to recover Au from discarded electric devices. This study investigated the effects of cyanide and dissolved oxygen concentration on biological Au recovery. Cyanide production by C. violaceum was sufficient to dissolve Au, while maintaining a high cyanide concentration did not enhance Au dissolution. Increased oxygen concentration enhanced Au dissolution from 0.04 to 0.16 mmol/l within the test period of 70 h. Electrochemical measurement clarified this phenomenon; the rest potential of Au in the cyanide solution produced by C. violaceum increased from -400 to -200 mV, while in the sterile cyanide solution, it was constant in cyanide concentrations ranging from 0 to 1.5 mmol/l and increased in dissolved oxygen concentrations ranging from 0 to 0.25 mmol/l. Therefore, it was clarified that dissolved oxygen concentration is the main factor affecting the efficiency of cyanide leaching of gold by using bacteria.

Biodegradation, Environmental↗
PubMed2005

Heterogeneous catalytic degradation of cyanide using copper-impregnated pumice and hydrogen peroxide.

The main objective of this research was to investigate the oxidative destruction of free cyanide with hydrogen peroxide and copper-impregnated pumice as a heterogeneous catalyst. Original or copper-impregnated pumices added alone were not effective adsorbents of negatively charged cyanide ions due to incompatible surface interactions. Peroxide and original pumices added together were also ineffective in removing cyanide. However, for all of the three natural pumices tested with various particle size fractions, the use of copper-impregnated pumices and peroxide together significantly enhanced both the initial rate and extent of cyanide removal. Although copper-impregnated specific surface area was the major factor affecting the rate and extent of cyanide destruction for a particular pumice source with similar surface chemistries, the type of surface chemistry (i.e., specific functional groups) within different pumice sources also appears to be a very important factor. Lower rates and extents of cyanide removals were observed at pH 11 compared to pH 8 probably because of the negative impacts of alkaline conditions in terms of scavenging peroxide and forming more negatively charged pumice surfaces. Both the initial rate and ultimate extent of cyanide removals were generally higher at a temperature of 20 degrees C compared with those found at 10 degrees C. The use of copper-impregnated pumice as a light, cheap, readily available, natural, and porous heterogeneous catalyst either in completely mixed/suspended or fixed-bed reactor configurations may be an effective treatment technology for cyanide removal from solution. This new approach may minimize downstream metal removal problems experienced in conventional cyanide oxidation technologies.

Catalysis↗
PubMed1998

Acute effects of acetyl-L-carnitine on sodium cyanide-induced behavioral and biochemical deficits.

In the present study we investigated the effects of acute treatment with acetyl-L-carnitine (50 mg/kg, i.v. 90 min before the sodium cyanide injection) on a sodium cyanide-induced behavioral deficit in the Morris water escape task. In a first experiment the spatial discrimination performance of the rats was found to be dose-dependently impaired after an i.c.v. injection of sodium cyanide (2.5 and 5.0 microg). Acute treatment with acetyl-L-carnitine was found to increase the behavioral deficit after sodium cyanide. These findings were replicated in a second experiment. Based on these results it can be argued that an acute administration of acetyl-L-carnitine appears to potentiate a sodium cyanide-induced behavioral deficit. An additional in vitro experiment with rat brain synaptosomes showed clear effects of administered sodium cyanide on the energy-dependent incorporation of inositol into phosphoinositides and on the ATP concentration. In vitro acetyl-L-carnitine administration had no effect on the sodium cyanide-induced energy depletion. The negative behavioral findings are in contrast with our previously found protective effect of chronic treatment with acetyl-L-carnitine (via drinking water) on the sodium cyanide-induced behavioral deficit. Since chronic acetyl-L-carnitine treatment has no effect on the phosphoinositide metabolism it was suggested that acetyl-L-carnitine may act via the formation of an ATP-independent reservoir of activated acyl groups. Thus, fatty acids as acylated derivatives can be used for reacylation processes during an acute period of energy depletion. However, we have no clear explanation for the discrepancy in behavioral results between the chronic vs acute treatment of acetyl-L-carnitine at present. Further research is needed to characterize the mechanism of action of acetyl-L-carnitine in relation to sodium cyanide.

Acetylcarnitine↗
PubMedDate not supplied

Artifacts in the definition of toxicity by cyanides and cyanogens.

Misleading conclusions may be drawn in defining toxicity from administered cyanides or cyanogens if meticulous attention to detail is not given in the design, conduct and interpretation of experimental and analytical procedures. Problems may occur if specimens are not appropriately stored or if interfering factors, such as antidotal agents, are present. Measurement of whole blood cyanide concentrations is valuable for diagnostic purposes, but plasma concentrations may give a better functional index of blood cyanide providing that samples are immediately analyzed. The most appropriate tissues for cyanide and cytochrome oxidase determinations are brain and ventricular myocardium. Analyses should be carried out immediately on freshly sampled tissue. In addition to the use of biochemical techniques for determination of cytochrome oxidase activity, dynamic quantitative histochemical methods are useful for assessing effects of cyanide on regional parenchymal enzyme activity. In determining cyanide-related cyanogen toxicity, the signs are useful, but comparison of molar lethal toxicity data requires caution. Confirmatory antidotal studies should be carefully designed with respect to both the nature and timing of antidotal procedures. In vitro studies assist in confirming cyanide liberation and are of value for investigating mechanisms of cyanogenesis. Variations in toxicity between cyanides and cyanogens are due to both the influence of inherent toxicity of the cyanogen molecule and differences in the rate of accumulation of biologically active cyanide.

Animals↗
PubMed1999

Liver and kidney lesions and associated enzyme changes induced in rabbits by chronic cyanide exposure.

The effect of prolonged chronic cyanide exposure on liver and kidney integrity, as well as some associated enzyme and metabolite changes, were investigated in New Zealand white rabbits (initial mean weight 1.52 kg) using a combination of colorimetric, spectrophotometric, enzymatic, gravimetric and histological procedures. Two groups of rabbits were fed for 40 weeks on either pure growers' mash or growers' mash containing 702 ppm inorganic cyanide. Results obtained indicate that the cyanide-fed rabbits had significantly decreased liver activities of alkaline phosphatase, glutamate pyruvate transaminase and sorbitol dehydrogenase relative to controls (P<0.05). On the other hand, there were significant increases (P<0.05) in the serum activities of these enzymes in the cyanide-treated group. Kidney alkaline phosphatase activity was significantly decreased (P<0.05), while serum urea and creatinine were significantly higher (P<0.05) in the cyanide group relative to controls. The cyanide treatment led to significant increases in both tissue and serum activities of lactate dehydrogenase. In addition, liver and kidney rhodanese activities were significantly raised in the cyanide-fed group. There were marked degenerative changes in the liver and kidney sections from the cyanide-treated rabbits. These results suggest that chronic cyanide exposure may be deleterious to liver and kidney functions.

Animals↗
PubMed1997

Dynamics of cyanide binding to ferrous Scapharca inaequivalvis homodimeric hemoglobin.

Flash photolysis experiments have been carried out for the first time on a hemoglobin ferrous cyanide adduct with an 8 ns laser pulse. A 95% nonexponential rebinding process occurs within 2 micros after full photolysis in ferrous cyanide dimeric Scapharca inaequivalvis hemoglobin (HbI), indicating that once photolyzed the cyanide anion is not able to escape from the protein matrix and rebinds to the heme iron. The resonance Raman spectrum of the 10 ns photoproduct is identical to that of the fully relaxed deoxy derivative, indicating that in the ferrous cyanide HbI adduct protein relaxation occurs within 10 ns after photolysis. This behavior is at variance with that of the carbonmonoxy HbI derivative in which very little geminate rebinding is observed and the photoproduct relaxes with a lifetime of 1 micros. The fast relaxation of the cyanide HbI photoproduct can be accounted for by the small perturbation of the heme structure induced by cyanide binding to ferrous HbI. This is consistent with a deoxy-like conformation of the HbI ferrous cyanide adduct and implies that the pathway for relaxation involves only minor local rearrangements of the heme moiety. Photolysis experiments carried out on ferrous cyanide horse myoglobin, which can be saturated only partially, show a qualitatively similar behavior in ligand rebinding, indicating that the geminate process of the cyanide anion is a general phenomenon in hemoproteins.

Animals↗
PubMed2001

Biogenic production of cyanide and its application to gold recovery.

Chromobacterium violaceum is a cyanogenic (cyanide-producing) microorganism. Cyanide is used on an industrial scale to complex and recover gold from ores or concentrates of ores bearing the precious metal. A potentially useful approach in gold mining operations could be to produce cyanide biologically in relatively small quantities at the ore surface. In this study, C. violaceum grown in nutrient broth formed a biofilm and could complex and solubilize 100% of the gold on glass test slides within 4-7 days. Approximately 50% of the cyanide- recoverable gold could be mobilized from a biooxidized sulfidic-ore concentrate. Complexation of cyanide in solution by gold appeared to have a beneficial effect on cell growth--viable cell counts were nearly two orders of magnitude greater in the presence of gold-coated slides or biooxidized ore substrates than in their absence. C. violaceum was cyanogenic when grown in alternative feedstocks. When grown in a mineral salt solution supplemented with 13.3% v/v swine fecal material (SFM), cells exhibited pigmentation and suspended cell concentrations comparable to cultures grown in nutrient broth. Glycine supplements stimulated production of cyanide in 13.3% v/v SFM. In contrast, glycine was inhibitory when added at the time of inoculation in the more concentrated SFM, decreasing cell numbers and reducing ultimate bulk-solution cyanide concentrations. However, aeration and addition of glycine to stationary phase cells grown on 13.3% v/v SFM anaerobically resulted in rapid production and high concentrations (up to 38 mg l(-1)) of cyanide. This indicates that biogenesis of cyanide may be supported in remote areas using locally produced and inexpensive agricultural feedstocks in place of commercial media.

Animals↗
PubMed2002

NF-kappaB-mediated up-regulation of Bcl-X(S) and Bax contributes to cytochrome c release in cyanide-induced apoptosis.

Cyanide induces apoptosis through cytochrome c activated caspase cascade in primary cultured cortical neurons. The underlying mechanism for cytochrome c release from mitochondria after cyanide treatment is still unclear. In this study, the roles of endogenous Bcl-2 proteins in cyanide-induced apoptosis were investigated. After cyanide (100-500 microm) treatment for 24 h, two pro-apoptotic Bcl-2 proteins, Bcl-X(S) and Bax were up-regulated as shown by western blot and RT-PCR analysis. The expression levels of two antiapoptotic Bcl-2 proteins, Bcl-2 and Bcl-X(L), remained unchanged after cyanide treatment, whereas the mRNA levels of Bcl-X(S) and Bax began to increase within 2 h and their protein levels increased 6 h after treatment. NF-kappaB, a redox-sensitive transcription factor activated after cyanide treatment, is responsible for the up-regulation of Bcl-X(S) and Bax. SN50, which is a synthetic peptide that blocks translocation of NF-kappaB from cytosol to nucleus, inhibited the up-regulation of Bcl-X(S) and Bax. Similar results were obtained using a specific kappaB decoy DNA. NMDA receptor activation and reactive oxygen species (ROS) generation are upstream events of NF-kappaB activation, as blockade of these two events by MK801, l-NAME or PBN inhibited cyanide-induced up-regulation of Bcl-X(S) and Bax. Up-regulation of pro-apoptotic Bcl-X(S) and Bax contributed to cyanide-induced cytochrome c release, because SN50 and a specific Bax antisense oligodeoxynucleotide significantly reduced release of cytochrome c from mitochondria as shown by western blot analysis. It was concluded that NF-kappaB-mediated up-regulation of Bcl-X(S) and Bax is involved in regulating cytochrome c release in cyanide-induced apoptosis.

Animals↗
PubMed2003

How does cyanide inhibit superoxide reductase? Insight from synthetic FeIIIN4S model complexes.

Superoxide reductases (SORs) are nonheme iron-containing enzymes that reduce HO(2) to H(2)O(2). Exogenous substrates such as N(3)(-) and CN(-) have been shown to bind to the catalytic iron site of SOR, and cyanide acts as an inhibitor. To understand how these exogenous ligands alter the physical and reactivity properties of the SOR iron site, acetate-, azide-, and cyanide-ligated synthetic models of SOR have been prepared. The x-ray crystal structures of azide-ligated [Fe(III)(S(Me2)N(4)(tren))(N(3))](+) (3), dimeric cyanide-bridged ([Fe(III)(S(Me2)N(4)(tren))](2)-mu-CN)(3+) (5), and acetate-ligated [Fe(III)(S(Me2)N(4)(tren))(OAc)](+) (6) are described, in addition to x-ray absorption spectrum-derived and preliminary crystallographic structures of cyanide-ligated [Fe(III)(S(Me2)N(4)(tren))(CN)](+) (4). Cyanide coordination to our model (4) causes the redox potential to shift anodically by 470 mV relative to acetate-ligated 6 and 395 mV relative to azide-ligated 3. If cyanide coordination were to cause a similar shift in redox potential with SOR, then the reduction potential of the catalytically active Fe(3+) center would fall well below that of its biological reductants. These results suggest therefore that cyanide inhibits SOR activity by making the Fe(2+) state inaccessible and thus preventing the enzyme from turning over. Cyanide inhibits activity in the metalloenzyme superoxide dismutase via a similar mechanism. The reduced five-coordinate precursor to 3, 4, and 6 [Fe(II)(S(Me2)N(4)(tren))](+) (1) was previously shown by us to react with superoxide to afford H(2)O(2) via an [Fe(III)(S(Me2)N(4)(tren))(OOH)](+) intermediate. Cyanide and azide do not bind to 1 and do not prevent 1 from reducing superoxide.

Azides↗
PubMed2004

Accumulation of cyanide and thiocyanate in haemodialysis patients.

BACKGROUND: Cyanide is a toxic agent, and its detoxification product, thiocyanate, may be a major pathogenetic substance in uraemia. Recent studies examining the myeloperoxidase(MPO)/thiocyanate system have suggested a link between thiocyanate and atherosclerosis. However, inaccuracies in conventional assays for cyanide and thiocyanate have limited the understanding of their metabolism in haemodialysis (HD) patients. METHODS: We used high-performance liquid chromatography to measure cyanide in erythrocytes and thiocyanate in plasma in 43 HD patients and in a group of 46 healthy controls that included 15 current smokers. To clarify the metabolic conversion of cyanide to thiocyanate in uraemic patients, we also measured cysteine and sulfate. We then used stepwise regression analysis to analyse factors that determine erythrocyte cyanide and plasma thiocyanate. RESULTS: Mean cyanide and thiocyanate were significantly greater in HD patients than in non-smoking controls. However, cyanide was far below lethal concentrations in dialysis patients. Thiocyanate was six to seven times greater in HD patients than in non-smoking controls, and decreases in thiocyanate following dialysis were only 19.3+/-3.5%. Multiple regression analysis showed a positive correlation between cyanide and thiocyanate in controls, but a negative correlation in HD patients. In patients, an inverse relationship between thiocyanate and BUN was also observed. CONCLUSIONS: The elevation of thiocyanate in patients undergoing dialysis probably is secondary to both limited efficiency of HD and deranged metabolism of cyanide and thiocyanate. Because thiocyanate is a preferred substrate for MPO, it may play a role in uraemic complications including cardiovascular events.

Adult↗