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At least 19 recordsLinked to original sources
PubMed1978

The mechanism of the mutagenic action of hydroxylamine XIII. Reversion of phage MS2 amber mutants in the presence of hydroxylamines.

The replication of the phage MS2 in the presence of either hydroxylamine (HA) or O-methylhydroxylamine (OMHA) (mutagenesis in vivo) results in an increase in the reversion frequency of two amber mutations in the maturation protein. When acting on the extracellular phage (mutagenesis in vitro) the mutagens do not affect the reversion frequency. The most probable mode of mutagenic action of the hydroxylamines on the vegetative MS2 phage involves the enzymic formation of modified precursors and their incorporation into RNA.

Coliphages↗
PubMed1975

Effects of hydroxylamine on the consequences of long-lasting administration of morphine in mice. II. Time course of the hydroxylamine effect on morphine tolerance.

Mice injected for 35 days with morphine sulfate in increasing doses did not show tolerance to the analgesic effects of morphine if injected intracranially with 0.3 M hydroxylamine. The excitatory action of morphine was unaffected. The interference with tolerance lasted for at least six weeks following the hydroxylamine injection. There were no apparent histological changes in the brains of treated mice as well as no differences in the composition of water-soluble brain proteins.

Animals↗
PubMed1978

The mechanism of the mutagenic action of hydroxylamine XII. Phenotypic suppression of amber mutants of phage T7 by hydroxylamine and O-methylhydroxylamine.

The reproduction of phage T7 in the presence of hydroxylamine (HA) (mutagenesis in vivo) results in the phenotypic suppression of some amber mutants. The presence of O-methylhydroxylamine (OMHA) results in a similar effect, indicating a similar mechanism for the action of the two compounds. Since the rate of reaction of mutagen with nucleoside residues under these conditions in negligibly low, one of the most plausible explanations of this effect is the enzymic formation of modified precursors and their incorporation into bacterial tRNAs or phage-induced RNA.

Coliphages↗
PubMed1977

Activation of guanylate cyclase in cerebral cortex of rat by hydroxylamine.

Hydroxylamine actived guanylate cyclase in particulate fraction of cerebral cortex of rat. Activation was most remarkable in crude mitochondrial fraction. When the crude mitochondrial fraction was subjected to osmotic shock and fractionated, guanylate cyclase activity recovered in the subfractions as assayed with hydroxylamine was only one-third of the starting material. Recombination of the soluble and the particulate fractions, however, restored guanylate cyclase activity to the same level as that of the starting material. When varying quantities of the particulate and soluble fractions were combined, enzyme activity was proportional to the quantity of the soluble fraction. Heating of the soluble or particulate fraction at 55 degrees for 5 min inactivated guanylate cyclase. The heated particulate fraction markedly activated guanylate cyclase activity in the native soluble fraction, while the heated soluble fraction did not stimulate enzyme activity in the particulate. The particulate fraction preincubated with hydroxylamine at 37 degrees for 5 min followed by washing activated guanylate cyclase activity in the soluble fraction in the absence of hydroxylamine. Further fractionation of the crude mitochondrial fraction revealed that the factor(s) needed for the activation by hydroxylamine is associated with the mitochondria. The mitochondrial fraction of cerebral cortex activated guanylate cyclase in supernatant of brain, liver, or kidney in the presence of hydroxylamine. The mitochondrial fraction prepared from liver or kidney, in turn, activated soluble guanylate cyclase in brain. Activation of guanylate cyclase by hydroxylamine was compared with that of sodium azide. Azide activated guanylate cyclase in the synaptosomal soluble fraction, while hydroxylamine inhibited it. The particulate fraction preincubated with azide followed by washing did not stimulate guanylate cyclase activity in the absence of azide. The activation of guanylate cyclase by hydroxylamine is not due to a change in the concentration of the substrate GTP, Addition of hydroxylamine did not alter the apparent Km value of guanylate cyclase for GTP. Guanylate cyclase became less dependent on manganese in the presence of hydroxylamine. Thus the activation of guanylate cyclase by hydroxylamine is due to the change in the Vmax of the reaction.

Animals↗
PubMed1987

Reactions of hydroxylamine with the electron-donor side of photosystem II.

The reaction of hydroxylamine with the O2-evolving center of photosystem II (PSII) in the S1 state delays the advance of the H2O-oxidation cycle by two charge separations. In this paper, we compare and contrast the reactions of hydroxylamine and N-methyl-substituted analogues with the electron-donor side of PSII in both O2-evolving and inactivated [tris(hydroxymethyl)aminomethane- (Tris-) washed] spinach PSII membrane preparations. We have employed low-temperature electron paramagnetic resonance (EPR) spectroscopy in order to follow the oxidation state of the Mn complex in the O2-evolving center and to detect radical oxidation products of hydroxylamine. When the reaction of hydroxylamine with the S1 state in O2-evolving membranes is allowed to proceed to completion, the S2-state multiline EPR signal is suppressed until after three charge separations have occurred. Chemical removal of hydroxylamine from treated PSII membrane samples prior to illumination fails to reverse the effects of the dark reaction, which argues against an equilibrium coordination of hydroxylamine to a site in the O2-evolving center. Instead, the results indicate that the Mn complex is reduced by two electrons by hydroxylamine, forming the S-1 state. An additional two-electron reduction of the Mn complex to a labile "S-3" state probably occurs by a similar mechanism, accounting for the release of Mn(II) ions upon prolonged dark incubation of O2-evolving membranes with high concentrations of hydroxylamine. In N,N-dimethylhydroxylamine-treated, Tris-washed PSII membranes, which lack O2 evolution activity owing to loss of the Mn complex, a large yield of dimethyl nitroxide radical is produced immediately upon illumination at temperatures above 0 degrees C. The dimethyl nitroxide radical is not observed upon illumination under similar conditions in O2-evolving PSII membranes, suggesting that one-electron photooxidations of hydroxylamine do not occur in centers that retain a functional Mn complex. We suggest that the flash-induced N2 evolution observed in hydroxylamine-treated spinach thylakoid membrane preparations arises from recombination of hydroxylamine radicals formed in inactivated O2-evolving centers.

Chlorophyll↗
PubMed1989

Hydroxylamine is a vasorelaxant and a possible intermediate in the oxidative conversion of L-arginine to nitric oxide.

Our objective was to determine whether hydroxylamine is a possible intermediate in the oxidative conversion of L-arginine to nitric oxide. Vasorelaxation by hydroxylamine is known to be mediated by nitric oxide. The vasorelaxant properties of hydroxylamine were examined using rat aortic rings and an isolated rat lung perfusion model. Hydroxylamine and acetylcholine were equally effective in relaxing norepinephrine-contracted intact aortic rings, whereas only hydroxylamine relaxed aortic rings with endothelium removed. This endothelium-independent vasorelaxation by hydroxylamine indicated that the hydroxylamine-converting enzyme is not localized solely within endothelial cells. Catalase, an enzyme known to oxidize hydroxylamine to nitric oxide, was present in homogenates of intact and endothelium-denuded rings. Cyanamide, another catalase substrate and a known precursor of nitroxyl (HNO), was not a vasorelaxant of aortic rings or of isolated, hypoxia-constricted lungs. These results suggest that free nitroxyl is not an intermediate in the oxidation of hydroxylamine to nitric oxide. An overall pathway for the oxidative conversion of L-arginine through an hydroxylamine intermediate to nitric oxide is proposed.

Acetylcholine↗
PubMed1976

Correlation between flash-induced oxygen evolution and fluorescence yield kinetics in the 0 to 16 mus range in Chlorella pyyrenoidosa during incubation with hydroxylamine.

Following flash excitation, oxygen pulses and fluorescence kinetics in the time range 0-16 mus were studied in the alga Chlorella pyrenoidosa during incubation with various concentrations of hydroxylamine. The obtained results could be explained considering four effects of hydroxylamine. 1. Hydroxylamine removes (reduces) oxidizing equivalents, generated in the water-splitting system by flash excitation. This process does not markedly affect the fluorescence yield kinetics between 0 and 16 mus following the ignition of a flash and reaches a constant rate within a few minutes, but possibly within a few seconds, after addition of hydroxylamine. In a sequence of flashes separated by dark time td, the steady-state oxygen yield in the flashes is exp(-ktd), the yield at td=0 being taken equal to 1, where k=(0.1 + beta[NH2OH])s-1, with [NH2OH] in mM and beta=0.6 mM-1, provided [NH2OH]greater than or equal to 0.5 mM. 2. An inhibition between Z, the physiological donor and the oxidized reaction center pigment P+ occurs, proceeding as exp (-kiti)where ti is the incubation time with hydroxylamine and ki=(alpha[NH2OH]) min-1, with [NH2OH] in mM and alpha=0.14 mM-1. This process not only inhibits oxygen evolution capability, but also decreases the amplitude of the fluorescence yield difference deltaphi=phi(16 mus)-phi(2 mus) induced by a flesh in the steady state. In a fraction of the reaction centers this inhibition occurs "immediately" after the addition of hydroxylamine. These observations, combined with the conslusion of Cheniae and Martin (1971, Plant Physiol. 47, 568-575) that the inhibition of the Hill reaction is related to the extraction of bound manganese indicate that the reaction between Z and P+ requires bound manganese. 3. In the inhibited centers a second donor for P+, D, connected to an entry site for the artificial electron donor hydroxylamine becomes apparent. 4. A flash-induced oxygen uptake signal was observed in the presence of hydroxylamine, which was shown to be caused by a system II reaction. The effects under (1) and (4) were reversed in the dark if hydroxylamine was removed by washing. The effects under (2) and (3) were reversed during illumination of a washed sample.

Chlorella↗
PubMed1977

Flash induced fluorescence kinetics in chloroplasts in the 20 microseconds-100 s time range in the presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea. Effects of hydroxylamine.

Flash induced variations of the fluorescence yield have been studied at 2 degrees C over a long time range (at 1 microseconds and from 20 microseconds to 3 min) in chloroplasts in the presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) with or without addition of hydroxylamine. 1. In the presence of DCMU, a polyphasic rise is observed. A first fast rise (less than 1 microseconds) is ascribed to the transfer of the positive charge from the primary Photosystem II donor Chl to a secondary donor Y. Two hypotheses are proposed to interpret the existence of the subsequent slower increase (t1/2 approximately equal to 70 microseconds) which then follows the initial fast rise. 2. The effects or various hydroxylamine concentrations have been studied with a sufficient incubation time to inactivate the secondary donors Y and Z. This inactivation leads to a complete inhibition of the ability to emit oxygen. Under these conditions, the initial fast rise (less than 1 microseconds) is inhibited as shown by den Haan, G.A., Duysens, L. N. M. and Egberts, D. J. N. (1974) Biochim. Biophs. Acta 368, 409-421, and the oxidized Chl+ is reduced by an auxiliary donor D. The slow fluorescence rise observed after destruction of Y and Z has a similar kinetic behaviour to that observed in the presence of DCMU only and is polyphasic. In the presence of 10 mM hydroxylamine, the constant rate of the back reaction k1 between Chl+ and the primary acceptor Q- is estimated to be approx. (135 microseconds)-1 while the transfer of the positive charge from Chl+ to D has a rate constant k2 of approx. (105 microseconds)-1. 3. In the presence of hydroxylamine concentrations higher than 10 mM, there appears a rise in the 1-20 microseconds range ascribed to a direct reduction of oxidized Chl+ by hydroxylamine. 4. In chloroplasts treated with 10 mM hydroxylamine for 15 min and washed afterwards, the rate constant k3 of the back reaction between D+ and Q- is estimated to be approx. (100 ms)-1 which leads to a value of about 700 for the equilibrium constant between Chl and D. Hydroxylamine added under these conditions is able to reduce D+. The rate constant k4 of this reduction is estimated to be (350 ms)-1 in 0.1 mM hydroxylamine.

Chlorophyll↗
PubMed1990

Thiol-dependent passive K: Cl transport in sheep red blood cells: X. A hydroxylamine-oxidation induced K: Cl flux blocked by diethylpyrocarbonate.

Hydroxylamine, a potent oxidizing agent used to reverse carbethoxylation of histidine by diethylpyrocarbonate, activated Cl-dependent K flux (K: Cl cotransport) of low K sheep red blood cells almost sixfold. When K: Cl cotransport was already stimulated by N-ethylmaleimide, hydroxylamine caused an additional twofold activation suggesting modification of sites different from those thiol alkylated. This conclusion was supported by the finding that hydroxylamine additively augmented also the diamide-induced K: Cl flux (Lauf, P.K. 1988. J. Membrane Biol. 101: 179-188) with dithiothreitol fully reversing the diamide but not the hydroxylamine effect. Stimulation of K: Cl cotransport by hydroxylamine was completely inhibited by treatment with diethylpyrocarbonate also known to prevent K: Cl cotransport stimulation by N-ethylmaleimide, both effects being independent of the order of addition. Hence, although the effect of carbethoxy modification of K: Cl flux cannot be reversed by hydroxylamine and thus excludes histidine as the target for diethylpyrocarbonate, our finding reveals an important chemical determinant of K: Cl cotransport stimulation by both hydroxylamine oxidation and thiol group alkylation.

Animals↗
PubMed1988

Oxidation of hydroxylamines to nitroxide spin labels in living cells.

In the presence of oxygen, cells can oxidize hydroxylamines, which are the products of the reduction of nitroxides in cells, back to nitroxides. Lipid-soluble hydroxylamines are oxidized much more rapidly than water-soluble ones, and most of this oxidation is inactivated by heat or trichloroacetic acid, indicating that the principal mechanism is enzyme-linked. The rates of oxidation of some lipophilic hydroxylamines are comparable to the rates of reduction of the corresponding nitroxides. Hydroxylamines formed by reduction of aqueous soluble nitroxides are not oxidized by cells, except for slight oxidation of some pyrrolidine derivatives. The latter is due to autoxidation. The kinetics of oxidation of reduced lipid-soluble nitroxides are all first-order with respect to hydroxylamines, regardless of the position of the nitroxide group along the carbon backbone, indicating that the oxidation occurs within the membrane. The oxidation of hydroxylamines in cells in inhibited by cyanide but not by antimycin A or SKF-525A. We also describe an effective method to oxidize hydroxylamines and follow this reaction; the method is based on the use of perdeuterated [15N]Tempone.

Affinity Labels↗
PubMed1989

Oxidation of cardiac myoglobin in vivo by sodium nitrite or hydroxylamine.

A non-vascularized fish heart model was used to assess the oxidation of cardiac myoglobin in vivo by compounds known to cause methemoglobinemia. Buffalo sculpin (Enophrys bison) were cannulated from the afferent branchial artery to permit repeated blood sampling and injected intraperitoneally with sodium nitrite, hydroxylamine or aniline. Methemoglobin was formed by sublethal levels of sodium nitrite or hydroxylamine. For hydroxylamine, the time to peak effect was less than 1 h. For sodium nitrite, the onset was less rapid and the effect more prolonged. Aniline had no effect on hemoglobin at any concentration tested. Cardiac myoglobin, assayed at the time of peak effect on hemoglobin, was oxidized in a dose-dependent manner by sodium nitrite or hydroxylamine. At high doses of sodium nitrite (50 and 100 mg/kg), the oxidation of myoglobin exceeded that of hemoglobin. The reverse was true of hydroxylamine at all concentrations tested. This study suggests that possibility that cardiac myoglobin is oxidized in occupational or other exposures to sodium nitrite, hydroxylamine and related compounds.

Animals↗
PubMed1977

Stimulation of isocitrate lyase biosynthesis by hydroxylamine and hydrazine.

Recently it has been demonstrated that hydroxylamine is an activator of triglyceride catabolism. We have studied the effect of hydroxylamine on isocitrate lyase activity and lipid catabolism and have noted a stimulation of isocitrate lyase biosynthesis by 5 mM hydroxylamine. The specificity of this effect was tested with a number of representative enzymes of other metabolic pathways. In an attempt to study the possible mechanism of action of hydroxylamine we have also tested the effects of two substances that are structural or functional analogues of hydroxylamine, namely, ethanolamine and hydrazine, both on the enzyme level in plant cultures and on the activity of enzyme preparations. From our data we may conclude that "de nove" biosynthesis of isocitrate lyase depends on the reaction of hydroxylamine or hydrazine with glyoxylate to give the corresponding oxime and hydrazone. The removal of glyoxylate from the biological equilibrium in this way could cause extra formation of isocitrate lyase.

Dose-Response Relationship, Drug↗
PubMed1992

Sulfation of hydroxylamines and hydroxamic acids in liver cytosol from male and female rats and purified aryl sulfotransferase IV.

Sulfation activity towards hydroxamic acids and hydroxylamines was determined in liver cytosols for juvenile and adult males and female rats, as well as in purified rat liver aryl sulfotransferase IV preparations. Sulfation activity towards the hydroxamic acids N-hydroxy-2-acetylaminofluorene, N-hydroxy-2-acetylaminophenanthrene, N-hydroxy-4-acetylaminobiphenyl, N-hydroxy-4'-fluoro-4-acetylaminobiphenyl, N-hydroxy-2-acetylamino-5-phenylpyridine, was higher in cytosols derived from adult males (two or three times) than in those from adult females and juveniles (both sexes). N-Hydroxy-2-acetylamino-3-methyl-5-phenylpyridine (N-OH-2AAMPP), however, was poorly sulfated by any of the cytosols. Sulfation activity towards the hydroxylamines N-hydroxy-2-aminofluorene, N-hydroxy-2-aminophenanthrene, N-hydroxy-4-aminobiphenyl, N-hydroxy-4'-fluoro-4-aminobiphenyl was much lower. N-Hydroxy-2-amino-5-phenylpyridine (N-OH-2APP), however, was sulfated much better than the other hydroxylamines. No higher sulfation activity in adult male cytosols for hydroxylamines was found, except for N-OH-2APP and N-hydroxy-2-amino-3-methyl-5-phenylpyridine (N-OH-2AMPP). Purified aryl sulfotransferase IV (AST IV) converted all hydroxamic acids; N-OH-2AAMPP was a poor substrate. Of the hydroxylamines only N-OH-2APP and N-OH-2AMPP were conjugated. These results suggest that hydroxylamines and hydroxamic acids are converted by different sulfotransferases in the rat in vivo. They also indicate that AST IV may be the major enzyme responsible for sulfation of a variety of aromatic hydroxamic acids in the male rat liver. The results presented here are discussed in relation to the carcinogenic effects of some of these compounds.

Aging↗
PubMed1989

Procainamide hydroxylamine lymphocyte toxicity--I. Evidence for participation by hemoglobin.

A number of lines of evidence suggest that the lupus-like symptoms associated with procainamide therapy may be caused by products of metabolic N-oxidation. In the present study, the perfusion of the isolated rat liver with a hemoglobin-free solution containing procainamide (100 microM) resulted in the rapid appearance of the N-oxidation metabolite procainamide hydroxylamine in the perfusate. Addition of procainamide hydroxylamine in vitro to whole rat blood (1-40 microM) resulted in a concentration-dependent loss of proliferative response among mononuclear cells isolated from the treated blood and cultured with mitogens (phytohemagglutinin, PHA-P: concanavalin A, Con A; and pokeweed mitogen, PWM), as well as a loss of viability. Similar effects on lymphocyte mitogen responsiveness were observed when procainamide hydroxylamine (1-40 microM) was added to rat whole splenic cell populations. Carbon monoxide or ascorbic acid pretreatment inhibited the toxicity of procainamide hydroxylamine to lymphocytes in whole blood, but only carbon monoxide pretreatment inhibited procainamide hydroxylamine-induced methemoglobin formation. These observations are consistent with the participation of hemoglobin in a redox cycle with procainamide hydroxylamine, generating products which are primarily responsible for its cytotoxicity in blood.

Acecainide↗
PubMedDate not supplied

The formation of procainamide hydroxylamine by rat and human liver microsomes.

A method is described, using HPLC and electrochemical detection, which permits the direct quantitation of procainamide hydroxylamine. Procainamide hydroxylamine was formed from procainamide by hepatic microsomes from both rat and human, with rat microsomes showing higher apparent formation rates. The apparent Km for formation of procainamide hydroxylamine was 0.044 mM for rat liver microsomes, with an apparent Vmax of 2.81 nmol/min/mg of protein. Estimates of Km from three human microsomal samples were 6.29, 2.89, and 6.88 mM. Vmax estimates were 0.31, 0.74, and 0.74 nmol/min/mg of protein, respectively, roughly an order of magnitude less than that observed for the rat. Microsomal formation in both species was inhibited by boiling the microsomes, eliminating NADPH from the incubation system, by preincubation with SKF 525A, cimetidine, or n-octylamine, or by gassing the microsomal incubation mixture with carbon monoxide. These observations suggest that procainamide hydroxylamine formation is cytochrome P-450 mediated. Procainamide hydroxylamine could not be detected in the blood of rats treated with a single dose of procainamide, 100 mg/kg, po. One potential reason for the inability to detect this metabolite in blood is indicated by the rapid disappearance in vitro of procainamide hydroxylamine added to whole blood. Most of this disappearance appears to be due to an interaction with hemoglobin.

Adult↗
PubMed1988

Cupric ion-dependent inhibition of lysosomal acid cholesteryl ester hydrolase in the presence of hydroxylamine.

In the presence of hydroxylamine or ascorbic acid, the inhibitory effects of Cu2+ on lysosomal acid cholesteryl ester hydrolase (acid CEH) partially purified from rat liver were studied. Hydroxylamine stimulated the inhibition of acid CEH activity by Cu2+ but not that by Zn2+, Fe2+, Co2+, Mn2+, Ca2+, Mg2+ and Hg2+. This Cu2+-dependent inhibition of acid cholesterol ester hydrolase (CEH) activity was completely prevented by ethylenediamine tetraacetic acid (EDTA), EGTA and o-phenanthroline, a chelator with a stability constant for Cu2+, and also by sulfhydryl agents and cytoplasmic reducing agents such as cysteine, glutathione and mercaptoethanol. In addition, the stimulative effects of hydroxylamine on Cu2+-dependent inhibition were maintained even after preincubation of Cu2+ with hydroxylamine. On the other hand, ascorbic acid was found to replace the stimulation by hydroxylamine of the Cu2+-dependent inhibition of acid CEH activity but the effects of ascorbic acid progressively became smaller with prolongation of the preincubation time. Moreover, addition of chemical radical scavengers to the reaction mixture did not prevent the Cu2+-dependent inhibition of acid CEH activity in the presence of ascorbic acid. These results suggest that Cu2+ causes inhibition of lysosomal acid CEH activity through the formation of Cu1+ in a reductive medium.

Animals↗
PubMed1990

The S0 state of photosystem II induced by hydroxylamine: differences between the structure of the manganese complex in the S0 and S1 states determined by X-ray absorption spectroscopy.

Hydroxylamine at low concentrations causes a two-flash delay in the first maximum flash yield of oxygen evolved from spinach photosystem II (PSII) subchloroplast membranes that have been excited by a series of saturating flashes of light. Untreated PSII membrane preparations exhibit a multiline EPR signal assigned to a manganese cluster and associated with the S2 state when illuminated at 195 K, or at 273 K in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). We used the extent of suppression of the multiline EPR signal observed in samples illuminated at 195 K to determine the fraction of PSII reaction centers set back to a hydroxylamine-induced S0-like state, which we designate S0*. The manganese K-edge X-ray absorption edges for dark-adapted PSII preparations with or without hydroxylamine are virtually identical. This indicates that, despite its high binding affinity to the oxygen-evolving complex (OEC) in the dark, hydroxylamine does not reduce chemically the manganese cluster within the OEC in the dark. After a single turnover of PSII, a shift to lower energy is observed in the inflection of the Mn K-edge of the manganese cluster. We conclude that, in the presence of hydroxylamine, illumination causes a reduction of the OEC, resulting in a state resembling S0. This lower Mn K-edge energy of S0*, relative to the edge of S1, implies the storage and stabilization of an oxidative equivalent within the manganese cluster during the S0----S1 state transition. An analysis of the extended X-ray absorption fine structure (EXAFS) of the S0* state indicates that a significant structural rearrangement occurs between the S0* and S1 states. The X-ray absorption edge position and the structure of the manganese cluster in the S0* state are indicative of a heterogeneous mixture of formal valences of manganese including one Mn(II) which is not present in the S1 state.

Chlorophyll↗