Metabolism Of Hydrazine Research Articles

Gut microbiome modulates the toxicity of hydrazine: a metabonomic study

The influence of gut microbiota on the toxicity and metabolism of hydrazine has been investigated in germ-free and 'conventional' Sprague Dawley rats using 1H NMR based metabonomic analysis of urine and plasma. Toxicity was more severe in germ-free rats compared with conventional rats for equivalent exposures indicating that bacterial presence altered the nature or extent of response to hydrazine and that the toxic response can vary markedly in the absence of a functional microbiome.

Molecular Modelling Analysis of the Metabolism of Hydrazine

Molecular Modelling Analysis of the Metabolism of Hydrazine

Hamster Monomorphic Arylamine N-Acetyltransferase: Expression in Escherichia coli and Purification

N-Acetylation is a major pathway in the metabolism of hydrazine and arylamine drugs, and has been associated with carcinogen bioactivation. Monomorphic hamster liver N-acetyltransferase (NAT1) cDNA was cloned from hamster liver cells by reverse transcriptase-coupled polymerase chain reaction. The determined nucleotide sequence was identical to that reported for NAT1. The NAT1 coding region was subcloned into the pG1 yeast expression vector, but cell extracts provided only transient acetyltransferase activity. In addition, cDNA was subcloned into the expression vectors pFLAG-ATS and pFLAG-MAC, The latter vectors encoded a tac promoter and appended a low-molecular weight (1 kDa) hydrophilic FLAG; marker peptide to the amino terminus of NAT1. Unexpectedly, periplasmic export of FLAG ATS-NAT1 by the ompA signal peptide of pFLAG-ATS proved to be detrimental to enzyme activity. High acetyltransferase activity, however, was obtained when the fusion protein was expressed in the cytosol. Enzyme purified to homogeneity by immunoaffinity chromatography exhibited substrate specificity comparable to that of the hamster-derived protein.

Studies on the disposition and metabolism of hydrazine in rats in vivo.

1. Rats were given various doses of hydrazine orally and their plasma and liver hydrazine levels were determined (at various times up to 270 min after dosing) by gas chromatography/mass spectrometry. 2. The increase in the peak plasma level and in the area under the plasma concentration-time curve (AUC) were not directly proportional to the dose. 3. The ratio of plasma to liver hydrazine varied with dose suggesting saturation of an uptake mechanism might be occurring. 4. In a separate experiment hydrazine was still detectable in the plasma and liver 24 h after dosing with hydrazine i.p. 5. Rats were given the same doses of hydrazine and urine was collected for 24 h after dosing and assayed for hydrazine and acetylhydrazine. The proportion of hydrazine and acetylhydrazine excreted declined with dose. 6. Liver samples were taken for histopathological examination 96 h after dosing. Only after the highest dose (81 mg kg-1) was there evidence of fatty liver, 96 h after a single dose, and a reduction in both liver and body weight.

Identification of novel hydrazine metabolites by 15N-NMR

15N-NMR has been used to study the metabolism of hydrazine in rats in vivo. Single doses of [ 15N 2]hydrazine (2.0 mmol/kg: 98.6% g atom) were administered to rats and urine collected for 24 hr over ice. A number of metabolites were detected by 15N-NMR analysis of lyophilized urine. Ammonia was detected as a singlet at 0 ppm and unchanged [ 15N 2]hydrazine was present in the urine detectable as a singlet at 32 ppm. Peaks were observed at 107 and 110 ppm which were identified as being due to the hydrazido nitrogen of acetylhydrazine and diacetylhydrazine, respectively. A resonance at 85 ppm was ascribed to carbazic acid, resulting from reaction of hydrazine with carbon dioxide. A singlet detected at 316 ppm was thought to be due to the hydrazono nitrogen of the pyruvate hydrazone. The resonance at 56 ppm was assigned to 15N-enriched urea, this together with the presence of ammonia indicates that the N-N bond of hydrazine is cleaved in vivo, possibly by N-oxidation, and the resultant ammonia is incorporated into urea. A doublet centred at 150 ppm and a singlet at 294 ppm were assigned to a metabolite which results from cyelization of the 2-oxoglutarate hydrazone. Therefore 15N-NMR spectroscoplc analysis of urine has yielded significant new information on the metabolism of hydrazine.

Spin trapping of a free radical intermediate formed during microsomal metabolism of hydrazine

A radical formed during oxidative metabolism of hydrazine in rat liver microsomes was spin-trapped with α-phenyl-t-butylnitrone. The trapped species was identified as hydrazine radical by comparison of its ESR parameters and mass spectrum with those of the adduct formed during CuCl 2 catalyzed oxidation of hydrazine. The requirement for oxygen and NADPH in the microsomal oxidation and the occurrence of a typical binding spectrum by difference spectroscopy suggest the involvement of the participation of the cytochrome P-450 enzyme system in the formation of hydrazine radical which must be a precursor of diimide during microsomal oxidation of hydrazine.

A free radical mediated cooxidation of tetramethylhydrazine by prostaglandin hydroperoxidase.

Prostaglandin endoperoxide synthase catalyzed the oxidation of tetramethylhydrazine to the tetramethylhydrazine radical cation, as detected by electron spin resonance spectroscopy. Oxidation of tetramethylhydrazine by prostaglandin endoperoxide synthase also resulted in the N-demethylation of tetramethylhydrazine leading to the formation of formaldehyde. Both the radical and formaldehyde formation were dependent on arachidonic acid, inhibited by indomethacin, and supported by 15-hydroperoxyarachidonic acid, indicating that the metabolism was peroxidative. We propose that tetramethylhydrazine undergoes two sequential one-electron oxidations yielding an iminium cation, which is then hydrolyzed to yield formaldehyde. Metabolism of hydrazines by prostaglandin endoperoxide synthase may be of importance in tissue containing low mixed-function oxidase activity.

Metabolism of hydrazines and hydrazides by the intestinal microflora.

Intestinal microorganisms are able to effect the metabolic reductive fission of hydrazines but not hydrazides during incubation in vitro.