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PubMed1980

Active uptake of propranolol by isolated rabbit alveolar macrophages and its inhibition by other basic amines.

Propranolol and other basic amines are concentrated by the lung. To test the possibility that the alveolar macrophage might participate in this process, the uptake of dl-[3H]propranolol was studied in macrophages isolated from healthy male rabbits. Uptake was time, temperature, and pH dependent and was reduced in the presence of inhibitors of cellular energy metabolism, such as sodium azide, iodoacetate, sodium cyanide and 2,4-dinitrophenol. It was abolished by sonication of the cell suspension. Scatchard plots suggested at least three uptake processes, one of which appeared to be partition. Uptake of dl-[3H]propranolol was inhibited equally by increasing concentrations of both the dextro- and the levo-isomers, as well as the racemate. It was also markedly inhibited by the lysomotropic agents, ammonium chloride and chloroquine, and by a number of tertiary amines including imipramine, chlorpromazine and methadone. Endogenous amines, including noreprinephrine, epinephrine and histamine had no effect on uptake. These observations suggest that uptake processes in the lung for exogenous basic amines may differ from those for endogenous amines. Although uptake of endogenous amines has been localized to the vascular endothelium, the lysosome may be one intracellular site of accumulation for exogenous amines.

Amines↗

PubMed1990

Evaluation of glass-cermet cores under cast crowns.

The goal of this study was to compare two core materials--glass-cermet and amalgam--in terms of crown retention when significant tooth structure is missing. The glass-cermet's ability to bond to teeth with and without the aid of retentive pins and/or grooves was examined. The effects of two storage solutions, formalin and sodium azide, on the bond of the glass-cermet were also evaluated. Sixty human molars were obtained and stored in either formalin or sodium azide. Thirty molars were prepared with one wall of tooth structure remaining, and the other 30 were prepared with two walls. Before being restored with glass-cermet, the preparations received either no retention, retentive grooves and pins, or retentive grooves only. Each preparation restored with amalgam received pins and grooves. Type III gold crowns were cemented in vitro with glass-ionomer luting agent, thermocycled 2500 times (5-50 degrees C), and then removed under a tensile force. The to amalgam and has adequate adhesion to the tooth, without additional retention, when at least two walls of the tooth remain. However, when only one wall of the tooth remains, the amalgam core is superior under tensile forces. There was a significant difference between the sodium azide and formalin storage solutions with regard to bond strength in one group (two walls, no pins, no grooves). In general, the cores placed on teeth stored in sodium azide exhibited tensile bond strengths lower than those stored in formalin.

Adhesiveness↗

PubMed2004

Determination of azide as the 3,5-dinitrobenzoyl derivative by capillary electrophoresis.

A simple, rapid and reliable capillary electrophoresis method with a photodiode array detector was developed for determination of azide as the 3,5-dinitrobenzoyl derivative in drink samples fortified with sodium azide. Sample preparation was simple and rapid because no more than a simple dilution of samples is needed after quick derivatization. Separation was carried out using a buffer system comprising 25 mM phosphate buffer and 4 mM cetyltrimethylammonium hydroxide at pH 3.0. Methyl benzoate was selected as the internal standard (IS). This study investigated the influence of the concentration of phosphate buffer and electroosmotic flow (EOF) modifier, and the buffer pH on migration time and signal response. The optimized method made it possible to determine azide within 5 min. The limit of detection was determined to be 1.9 microg/ml with SIN > 3. The quantitation range was 6.5-323 microg/ml. By the method recoveries of azide in drink samples fortified with sodium azide were investigated. Mean recovery values ranged from 93.6 to 105.8% and results were satisfactory. In addition, no interference was observed in electropherograms of drink samples fortified with sodium azide. Thus, by this method, azide in drink samples can be determined rapidly with high recoveries and good selectivity despite extremely simple sample preparation.

Azides↗

PubMed1976

Stimulation of the sodium pump by azide and high internal sodium: changes in the number of pumping sites and turnover rate.

1. The effects of 5 mM azide on [3H]ouabain uptake and 22Na efflux were determined. Both glycoside uptake and 22Na efflux were enhanced by azide. 2. Azide stimulated the Na pump in muscles whose pumping sites had been inhibited by ouabain and then transferred to a glycoside-free solution. This stimulation was observed before detecting any recovery of the initial pumping activity. 3. When both the resting and the azide-stimulated 22Na efflux had been blocked by ouabain, an additional exposure to azide, in a ouabain-free solution, had no further effects on 22Na efflux. 4. It is concluded that the increase in Na pumping caused by azide is due in part to an increase in the number of pumping sites. 5. [3H]ouabain binding was measured in muscles with different intracellular alkali cation concentrations. Variations in [Na]i from 15 up to 50 mM did not significantly affect the amount of glycoside bound. A substantial increase in binding occurred when [Na]i reached 70 mM. 6. It is proposed that the increase in Na extrusion that occurs during the recovery of Na loaded muscles mostly results from an increased turnover rate of the pump rather than from an increase in number of pumping sites.

Animals↗

PubMed1989

Effects of azide on gastric mucose.

Sodium azide, a classical inhibitor of cytochrome oxidase, is an effective inhibitor of gastric acid secretion in bullfrog and skate gastric mucosae at low concentrations. While a portion of the oxygen uptake in these tissues is sensitive to azide (KI less than 2 mM), there remains a large fraction (25-60%) with a KI more than 10 times this value, suggesting the presence of a second oxidase. The spectra of cytochromes c and b change with oxygen-nitrogen alternation in the presence of high azide concentrations which essentially eliminate the reactivity of cytochrome oxidase. In both species two additional components are observed in the spectra. The first has a peak at 590 nm, is not the cytochrome oxidase-CO complex, is fully reactive in the presence of azide and accounts for the asymmetry of the oxidase peak. The second is a component at 557 nm which can only be separated from cytochromes c and b by spectral deconvolution, and seems to react in a manner similar to cytochrome c. It is suggested that the 590 compound may be the alternate cytochrome oxidase.

Animals↗

PubMed1990

Synergy between penicillin and gentamicin against enterococci.

The role of active uptake in aminoglycoside activity against penicillin-treated enterococci was studied by viable counts and ATP determinations. Penicillin and gentamicin gave synergistic bactericidal and post-antibiotic effects (PAEs) which were partially reduced by sodium azide, an electron transport inhibitor, and totally blocked in the presence of both sodium azide and EDTA, which chelates divalent cations. EDTA and gentamicin showed marked synergy in both 'killing curve' and PAE experiments. This synergy was completely inhibited by sodium azide. The data indicate that the activity of gentamicin against enterococci that have been damaged by penicillin or EDTA is energy-dependent. This is consistent with present theories of gentamicin uptake via transportation drive by a protonmotive force.

Adenosine Triphosphate↗

PubMed2003

Relationships between respiration and susceptibility to azole antifungals in Candida glabrata.

Over the past two decades, the incidence of infections due to Candida glabrata, a yeast with intrinsic low susceptibility to azole antifungals, has increased markedly. Respiratory deficiency due to mutations in mitochondrial DNA (mtDNA) associated with resistance to azoles frequently occurs in vitro in this species. In order to specify the relationships between respiration and azole susceptibility, the effects of respiratory chain inhibitors on a wild-type isolate of C. glabrata were evaluated. Respiration of blastoconidia was immediately blocked after extemporaneous addition of potassium cyanide, whereas a 4-h preincubation was required for sodium azide. Antifungal susceptibility determined by a disk diffusion method on Casitone agar containing sodium azide showed a significant decrease in the susceptibility to azoles. Biweekly subculturing on Casitone agar supplemented with sodium azide was therefore performed. This resulted after 40 passages in the isolation of a respiration-deficient mutant, as suggested by its lack of growth on glycerol-containing agar. This respiratory deficiency was confirmed by flow cytometric analysis of blastoconidia stained with rhodamine 123 and by oxygraphy. Moreover, transmission electron microscopy and restriction endonuclease analysis of the mtDNA of mutant cells demonstrated the mitochondrial origin of the respiratory deficiency. Finally, this mutant exhibited cross-resistance to all the azoles tested. In conclusion, blockage of respiration in C. glabrata induces decreased susceptibility to azoles, culminating in azole resistance due to the deletion of mtDNA. This mechanism could explain the induction of petite mutations by azole antifungals which have been demonstrated to act directly on the mitochondrial respiratory chain.

Antifungal Agents↗

PubMed1983

Cyanide prevents the inhibition of platelet aggregation by nitroprusside, hydroxylamine and azide.

Sodium cyanide (CN-) in concentrations of 10 uM or more prevented the inhibition of epinephrine (2.5 uM) and of ADP (4.0 uM) induced primary and secondary aggregation brought about by 10 uM sodium nitroprusside (SNP). Cyanide alone in the same concentration had no effect on platelet aggregation induced by epinephrine or ADP. Even when the addition of CN- was delayed for as long as 9 min after epinephrine and SNP, it immediately reversed the SNP block and initiated a bimodal wave of aggregation. The effect of CN- on SNP inhibition of platelet aggregation appears to be competitive and reversible. Although they are less potent inhibitors of platelet aggregation than SNP, the effects of hydroxylamine (HA) and azide were also prevented by SNP. In our hands, sodium nitrite did not inhibit platelet aggregation consistently. The inhibitory effects of glyceryl trinitrate, papaverine and nitric oxide hemoglobin on platelet aggregation were not prevented by CN-. These interactions probably have no significance in vivo, but they indicate that SNP, HA and azide act on platelets and on vascular smooth muscle by similar or identical biochemical mechanisms. They also suggest that there are at least two sub-classes of so-called nitric oxide vasodilators. The effect of CN- may be mediated through an inhibition of the formation of nitric oxide from SNP, HA and azide.

Azides↗

PubMedDate not supplied

[Modelling of Mg2+, ATP-dependent mitochondrial Ca ions transport in smooth muscle cells using protonophore CCCP-sensitive fluorescent tetracycline].

Mg2+, ATP-dependent Ca2+ accumulation in the rat myometrial mitochondria was investigated in complex experiment using Ca2+ isotope (45Ca2+) and Ca(2+)-sensitive label tetracycline. Monotonous increase of the fluorescence signal, insensitive to thapsigargin (100 nM) was observed with following establishing the stationary state of incubation at 2 min. which correlates with results obtained using isotope technique. Experiments with isotope label signify, that protonophore CCCP, ruthenium red and sodium azide, in concentration 1 microM, 10 microM and 10 mM respectively, totally inhibits the accumulation of the Ca ions in mitochondria. At the same time, in conditions of Mg2+, ATP-dependent Ca2+ accumulation modeling in these cellular structures, CCCP and sodium azide, used in the same concentration, diminished tetracycline fluorescence signal increase. In the same conditions, the introduction of the CCCP (1 mM) into the incubation medium at 75 sec. after initiation of the transport process induced reversible quenching of the tetracycline fluorescence signal to the level, observed in case of initial CCCP presence in the medium. According to data obtained in the experiment, using Ca2+ isotope, Ca(2+)-ionophore A-23187 induces both the reversible release of previously accumulated Ca ions, and cause reversible quenching of the tetracycline fluorescence signal to the level, observed in case of initial CCCP (1 mM) and sodium azide (10 mM) presence in the incubation medium. Conclusion was drawn that the thapsigargin-insensitive and CCCP, sodium azide and A-23187-sensitive tetracycline fluorescence increasing in case of modeling of Mg2+, ATP-dependent Ca2+ accumulation in myometrial mitochondria reflect the Ca2+ uniporter functioning in those subcellular structures.

Animals↗

PubMedDate not supplied

A novel ATP-diphosphohydrolase from human term placental mitochondria.

This report describes an ATP-diphosphohydrolase activity associated with the inner membrane of human term placental mitochondria. An enriched fraction containing 30 per cent of the total protein and 80 per cent of the total ATP-diphosphohydrolase activity was obtained from submitochondrial particles. ATP-diphosphohydrolase activity was characterized in this fraction. The enzyme had a pH optimum of 8 and catalysed the hydrolysis of triphospho- and diphosphonucleosides other than ATP or ADP. Pyrophosphate was also hydrolysed, but AMP or other monoester phosphates were not. The activity of ATP-diphosphohydrolase was dependent on Mg(2 + ), Ca(2 + )or Mn(2 + )and the enzyme substrate was the cation-nucleotide complex. An excess of free cation produced inhibition.ATP-diphosphohydrolase activity was stimulated at micromolar concentrations of calcium or magnesium in the presence of La-PPi. Negative cooperativity kinetics was observed with all substrates tested. The V(max)ranged from 150 to 300nmol of Pi released/mg/min. The [S](0.5)for nucleotides was 1-10m m and 182m m for PPi. The enzyme was inhibited by orthovanadate, but not by l -phenylalanine, oligomycin, sodium azide, P(1),P(5)-di(adenosine-5')pentaphosphate or sodium fluoride.The experimental evidence showing absence of inhibition by sodium azide and sodium fluoride, hydrolysis of pyrophosphate but not of monoester phosphates, and negative cooperativity suggested that this enzyme was a novel ATP-diphosphohydrolase.

Apyrase↗

PubMed1983

Pyridine nucleotides of rabbit cornea with histotoxic anoxia: chemical analysis, non-invasive fluorometry and physiological correlates.

The pyridine nucleotides from both the epithelium and the endothelium of rabbit cornea were measured by the cycling assay. Sodium azide (10 mM) applied for 1 hr to induce histotoxic anoxia decreased the endothelial NAD+/NADH ratio from 4.62 to 1.49 and decreased the epithelial NAD+/NADH ratio from 2.56 to 1.08. The larger NAD+/NADH ratio for the endothelium as compared to the epithelium corresponds to a more oxidized state. The corresponding ratios for NADP+/NADPH were 1.2 for the endothelium and 0.70 for the epithelium. Sodium azide had no effect on the NADP+/NADPH ratio for the endothelium, but decreased the epithelial ratio to 0.62. Pyridine nucleotide fluorescence was measured with a difference corneal fluorometer on the perfused whole cornea preparation and the perfused everted corneal preparation. Sodium azide (10 mM) for 30 min resulted in a 19.4 +/- 0.7% increase in the pyridine nucleotide fluorescence from the whole corneal preparation and a 4.5 +/- 0.6% increase from the everted endothelial preparation. Corneal anoxia induced by stopping the perfusion on the endothelial side resulted in a 18.7 +/- 0.6% increase in pyridine nucleotide fluorescence for the whole corneal preparation. Sodium azide (10 mM) resulted in a 35% decrease in the transendothelial potential difference and a 76% decrease in the rate of transendothelial fluid transport. A comparison is made between invasive chemical analysis and real time, non-invasive fluorometry to measure histotoxic corneal anoxia.

Animals↗

PubMed1997

Energetic requirement of insulin secretion distal to calcium influx.

A number of agents that inhibit oxidative phosphorylation by different mechanisms (carbonyl cyanide mchlorophenylhydrazone [CCCP], sodium azide, oligomycin) induced an increase of cytoplasmic Ca2+ concentration ([Ca2+]i) in pancreatic beta-cells, as measured by microfluorimetry with digital imaging. All three agents are known inhibitors of insulin secretion, and the secretory response to 20 mmol/l glucose was found to be abolished in spite of elevated [Ca2+]i. Two reasons could account for this dissociation between increase of [Ca2+]i and insulin secretion: 1) the increase did not take place at a site critical for exocytosis, 2) a threshold concentration of a metabolism-derived factor like ATP exists for the induction of exocytosis. The increase of [Ca2+]i by CCCP and sodium azide involved release of Ca2+ from internal stores, whereas oligomycin induced a slow D 600-inhibitable Ca2+ influx. Because CCCP and sodium azide, but not oligomycin, decreased the mitochondrial membrane potential concomitantly with the increase of [Ca2+]i, release of Ca2+ from the mitochondria most probably plays a decisive role for the internal mobilization. A Ca2+ influx induced by 40 mmol/l K+ or 250 micromol/l tolbutamide was unimpaired in the presence of oligomycin, but oligomycin completely abolished insulin secretion in response to these agents. While CCCP and sodium azide opened ATP-sensitive K+ channels, oligomycin was virtually ineffective, although it could be shown to significantly reduce beta-cell ATP production. By comparison of the effects of different inhibitors of oxidative phosphorylation, we conclude that the initiation of exocytosis in beta-cells is particularly sensitive to a decrease of energy metabolism, more than ATP-sensitive K+ channels or voltage-dependent Ca2+ channels. Thus, any increase of [Ca2+]i in beta-cells that occurs in a situation of a decreased ATP supply is unlikely to elicit a secretory response.

Animals↗

PubMed2001

Azide inhibits human cytochrome P -4502E1, 1A2, and 3A4.

BACKGROUND: Recently, we showed that, in addition to cytochrome P-4502E1 (CYP2E1), CYP1A2 and CYP3A4 also contribute to the microsomal ethanol oxidizing system (MEOS). When MEOS activity is measured, sodium azide commonly is used to block the contaminating catalase. However, although CYP2E1 is considered insensitive to azide, its effect on the other P-450s is unknown. Therefore, the aim of the present study was to determine the effect of azide on human recombinant and hepatic CYP2E1, CYP1A2, and CYP3A4. METHODS AND RESULTS: Concentrations of sodium azide as low as 0.1 mM markedly inhibited the specific ethanol oxidation (mean +/- SEM) by recombinant CYP1A2 and CYP3A4 expressed in HepG2 cells (to 16 +/- 1% and 22 +/- 2% of control without azide, respectively; p < 0.01). By contrast, the specific activity of CYP2E1 was only slightly (and not significantly) inhibited at this azide concentration (to 79 +/- 12% of control). Similarly, in human liver microsomes (n = 6), 0.1 mM azide strongly inhibited CYP1A2-dependent (to 25 +/- 2%) and CYP3A4-dependent (to 15 +/- 2%) ethanol oxidation, whereas CYP2E1 was inhibited only at 10 mM azide (to 60 +/- 10%). Azide also strongly affected the apparent kinetic values of all three isoenzymes. Furthermore, azide inhibited the specific monooxygenase activities, both by recombinant and microsomal P-450s. CYP2E1-specific p-nitrophenol hydroxylation was the most sensitive to azide, whereas CYP1A2-dependent 7-methoxyresorufin O-dealkylation was only slightly inhibited. Judging from its effect on p-nitrophenol hydroxylation by human liver microsomes, the inhibition of azide was competitive (Ki 0.09 mM). CONCLUSIONS: Sodium azide at a concentration as low as 0.1 mM inhibited ethanol oxidation by CYP1A2 and CYP3A4. With CYP2E1, although oxidation of 50 mM ethanol was not inhibited by 0.1 mM azide, higher azide concentrations were inhibitory and 0.1 mM azide seemed to affect the kinetics of ethanol oxidation by CYP2E1. Therefore, azide should be avoided when measuring the MEOS activity because it may lead to underestimation, especially of CYP1A2- and CYP3A4-dependent ethanol oxidation.

Binding, Competitive↗

PubMed2001

Protein kinase C agonists enhance phagocytosis of P. aeruginosa by murine alveolar macrophages.

Pulmonary alveolar macrophages (AMphis) are incompetent to phagocytose unopsonized Pseudomonas aeruginosa, but ingestion by other macrophage phenotypes (i.e., peritoneal macrophages) occurs efficiently. The purpose of this study was to explore factors that might control such phenotypic differences. Our laboratory has demonstrated that AMphis exposed to sodium azide display enhanced phagocytosis of P. aeruginosa. Here we report that the phagocytic-enhancing effect of sodium azide was abrogated by inhibitors of protein kinase C (PKC). Furthermore, the addition of PKC agonists, such as phorbol myristate acetate (PMA), and tumor necrosis factor alpha (TNF-alpha), mimicked the phagocytic enhancing effect of sodium azide. We conclude that AM4phis are normally incompetent to phagocytose P. aeruginosa. Factors that up-regulate AMphi function (azide, PMA, TNF-alpha) can reverse the phagocytic incompetence in vitro. Although these compounds are not appropriate candidate therapeutic agents, their effects provide insights for understanding of the pathways responsible for regulation of P. aeruginosa phagocytosis.

Animals↗

PubMed2005

Microplates with integrated oxygen sensors for kinetic cell respiration measurement and cytotoxicity testing in primary and secondary cell lines.

This paper presents a cytotoxicity and cell respiration assay that is nondestructive and kinetic. It makes use of 96-well microplates integrated with oxygen sensors. The oxygen signal monitored on-line gives an indication of the cell viability. We show its application for suspension cell lines (Chinese hamster ovary and HL60 cells) as well as adherent (Caco2 cells) and primary (rat hepatocytes) cells using well-known cytotoxic compounds (sodium azide, diclofenac, clozapine, sodium dodecyl sulfate, 2-thiouracil, tamoxifen, and tranylcypromine). The 50% lethality concentration (LC50) obtained from the assay is compared with the standard 3-(4,5-dimethylthiazol-2- yl)-2,5-diphenyl-2H-tetrazolium bromide end-point assay. The cells can be grown directly in the plates, and the assay requires no further reagents or processing. The cells can be harvested for further analysis, if required. The on-line dynamic measurement allows the calculation of LC50 as a function of exposure time. LC50 was shown to decrease with time in HL60 cells. The dynamics of this process was considerably different for the three compounds sodium dodecyl sulfate, tamoxifen, and diclofenac, indicating a large potential of application of this method for cell death studies. The assay system can be applied to almost any cell-based systems with little adaptation. The assay is robust, flexible, and applicable for medium- to high-throughput systems requiring only minimal handling and no additional agent.

Animals↗

PubMed1997

Purification and characterization of a manganese-containing superoxide dismutase from a carboxydobacterium, Pseudomonas carboxydohydrogena.

Superoxide dismutase from Pseudomonas carboxydohydrogena, a carboxydobacterium, grown on carbon monoxide was purified 37.6-fold in seven steps to homogeneity, with a yield of 1.4%. The final specific activity was 2,396 units per mg protein as determined by an assay based on a 50% decrease in the rate of cytochrome c reduction. The molecular weight of the native enzyme was determined to be 42,500. Sodium dodecyl sulfate gel electrophoresis revealed two identical subunits of molecular weight 21,700. The optimal pH for enzyme activity was found to be 9.0. The enzyme was stable to heat treatment. The isoelectric point of the native enzyme was found to be 7.1. The enzyme showed an absorption peak at 280 nm with a shoulder at around 289 nm. Sodium azide, but not sodium cyanide and hydrogen peroxide, was found to inhibit the enzyme activity. One mol of native enzyme was found to contain 1.09 g-atom of manganese. Analysis of amino acid composition revealed that the enzyme contains cysteine. The superoxide dismutase of P. carboxydohydrogena was found to have antigenic sites identical to those of Oligotropha carboxydovorans. The enzyme showed partial identity to Hydrogenophaga pseudoflava and Escherichia coli enzymes, but no identity to Acinetobacter sp. strain JC1 enzyme.

Amino Acids↗

PubMed1999

Cytotoxic potential of the phytochemical genistein isoflavone (4',5',7-trihydroxyisoflavone) and certain environmental chemical compounds on testicular cells.

The effects of genistein (Gn), sodium azide (naz), and dexamethasone (dxm) on testicular cells TM3, TM4 and GC-1 spg were studied in vitro. First, a series of experiments were performed to assess the response of the cells to the exposure of Gn, naz, dxm, a combination of Gn with naz and Gn with dxm. Trypan blue exclusion assay was used to determine the percentage of viability, and LDH-cytotoxicity test was used to assess the degree of treatment-induced cytotoxicity on each cell type. A second series of experiments were performed to study cytomorphology and determine the type and percentage of treatment-induced cell death (apoptosis and necrosis) on each cell line, using fluorescent dye technique to detect apoptotic and necrotic cells, and tunnel assay to confirm apoptosis. The results from the data obtained demonstrated: i) that incubation of testis cells with each of the agents (Gn, dxm, naz) alone and in two combinations (Gn-dxm, and Gn-naz) induced significant testicular cell death; ii) that both genistein and dexamethasone mostly and significantly induced apoptotic cell death while sodium azide induced necrotic cell death; iii) that addition of dexamethasone to genistein demonstrated synergism in apoptosis on testis cells; and iv) that combination of naz with Gn demonstrated synergism in necrosis on testis cells even though Gn alone did not induce significant necrosis. It is concluded that the synergistic actions of genistein and dxm, and of genistein + sodium azide in induction of apoptosis and/or necrosis may be of clinical and pathophysiological research interest considering the chemopreventive and chemotherapeutic potential of genistein; and the clinico-pharmacological application of dexamethasone and sodium azide.

Animals↗

PubMed1985

[Inactivation of cytochrome P-450 in hydroxylase reactions].

It has been shown that sodium azide, a catalase inhibitor, accelerates the inactivation of cytochrome P-450 in reactions of hydroxylation of type I substrates, e.g., dimethylaniline (DMA), aminopyrine (AP), benzphetamine (BPh), p-nitroanisole (p-Na) and type II substrates--aniline (AN). In the absence of sodium azide, cytochrome P-450 is either non-activated (as in the case of AN) or is inactivated at a low rate. Haemoprotein inactivation in the presence of sodium azide in all hydroxylation reactions with the exception of O-demethylation of p-NA is a first-order reaction with respect to cytochrome P-450. Studies on the mechanism of cytochrome P-450 inactivation demonstrated that hydrogen peroxide formed via the NADPH-dependent hydroxylase cycle exhibits an inactivating effect towards the enzyme. The value of inactivation constant for cytochrome P-450 in hydroxylation reactions proceeding in the presence of sodium azide coincides with that of enzyme inactivation in the NADPH-oxidase and glucose oxidase systems generating H2O2.

Animals↗