ABSTRACT
Activation of 1,2-dimethylhydrazine (DMH) by prolonged auto-oxidation (24-h) induced proliferation of mouse fibroblasts at low hydrazine concentrations (0.1-1.0 mM) as determined by [3H-methyl]-thymidine uptake of confluent quiescent cells. Incubations were performed under conditions in which alkyl radicals are slowly formed by DMH auto-oxidation. The proliferative stimulus induced by DMH auto-oxidation complements that induced by insulin, PMA, and EGF. Inhibition by the iron chelators, o-phenanthroline and desferrioxamine, demonstrates that the induction of the proliferative effect is dependent on simple iron complexes. Proliferation was also inhibited by superoxide dismutase, catalase, and mannitol, implicating reactive oxygen species, although superoxide dismutase and catalase also inhibited alkyl radical formation, as determined by spin-trapping. These results suggest that cell proliferation induced by DMH auto-oxidation is mediated by reactive oxygen species, mainly the hydroxyl radical, and is dependent on simple iron complexes, possibly involving the Fenton reaction.
Subject(s)
Cell Division/drug effects , Dimethylhydrazines/pharmacology , Iron/metabolism , 1,2-Dimethylhydrazine , Animals , Carcinogens/pharmacology , Catalase/metabolism , Catalase/pharmacology , Cell Line , Chelating Agents/pharmacology , DNA/biosynthesis , Dimethylhydrazines/metabolism , Epidermal Growth Factor/pharmacology , Free Radical Scavengers/pharmacology , Free Radicals , Insulin/pharmacology , Mannitol/pharmacology , Mice , Mutagens/pharmacology , Oxidation-Reduction , Pentetic Acid/pharmacology , Reactive Oxygen Species/metabolism , Superoxide Dismutase/metabolism , Superoxide Dismutase/pharmacologyABSTRACT
The neutrophil-catalyzed metabolism of hydrazine derivatives to carbon-centered radicals was investigated by the spin-trapping technique using alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN). Oxidation of methylhydrazine (MeH), dimethylhydrazine (DMH), phenylethylhydrazine or procarbazine by neutrophils from rat peritoneal exudates led to the formation of alkyl radicals. The monosubstituted hydrazine oxidation by phorbol ester (PMA)- or Zymocel-activated neutrophils generated, on average, 2- to 4-fold more POBN-alkyl adducts than di-substituted hydrazines. Supernatant from sonicated neutrophils generated similar yields of radicals. Azide, an inhibitor of myeloperoxidase, effectively reduced the neutrophil-catalyzed radical yield from the oxidation of MeH but not DMH. On the other hand, superoxide dismutase and catalase effectively inhibited radical formation in DMH metabolism by PMA-activated neutrophils, in contrast to MeH metabolism. Our results show that neutrophils are able to metabolize hydrazine derivatives, the pathway depending on the hydrazine substitution. Alkyl radical production during the oxidation of mono-substituted derivatives, such as MeH, was mediated mainly by myeloperoxidase, and that of di-substituted derivatives, such as DMH, was mediated mainly by active oxygen species.
Subject(s)
Hydrazines/metabolism , Neutrophils/metabolism , 1,2-Dimethylhydrazine , Animals , Azides/pharmacology , Dimethylhydrazines/metabolism , Female , Free Radicals , L-Lactate Dehydrogenase/metabolism , Monomethylhydrazine/metabolism , Nitrogen Oxides , Peritoneal Cavity , Peroxidase/metabolism , Procarbazine/metabolism , Pyridines , Rats , Rats, Wistar , Reactive Oxygen Species/metabolism , Tetradecanoylphorbol AcetateABSTRACT
Spin-trapping experiments demonstrate that oxidation of 1,2-dimethylhydrazine and 2-phenylethylhydrazine generates a comparable yield of carbon-centered radicals when catalyzed by horseradish peroxidase - H2O2. Using oxyhemoglobin as the catalyst, 2-phenylethylhydrazine oxidation generates ten times more carbon-centered radicals than 1,2-dimethylhydrazine oxidation. This result is in agreement with oxygen consumption studies from which the apparent KM values of 8.0 mM and 72 mM were calculated for the oxyhemoglobin-catalyzed oxidation of 2-phenylethylhydrazine and 1,2-dimethylhydrazine, respectively. These differences in metabolic activation of mono- and disubstituted hydrazines may be of importance regarding the carcinogenic properties of these derivatives.
Subject(s)
Dimethylhydrazines/metabolism , Horseradish Peroxidase/metabolism , Methylhydrazines/metabolism , Oxyhemoglobins/metabolism , Peroxidases/metabolism , Phenylhydrazines/metabolism , 1,2-Dimethylhydrazine , Chemical Phenomena , Chemistry , Enzyme Activation , Free Radicals , Hydrogen-Ion Concentration , Oxidation-ReductionABSTRACT
Spin-trapping experiments demonstrate that oxidation of 1,2-dimethylhydrazine and 2-phenylethylgydrazine generates a comparable yield of carbon-centered radicals when catalyzed by horseradish peroxidase-H2O2. Using oxyhemoglobin as the catalyst, 2-phenylethylgydrazine oxidation generates ten times carbon-centered radicals than 1,2-dimethylhidrazine oxidation. This results is in agreement with oxygen consumption studies from which the apparent KM values of 8.0 mM and 72 mM were calculated for the oxyhemoglobin-catalyzed oxidation of 2-phenylethylhydrazine and 1,2-dimethylhydrazine, respectively. These differences in metabolic activation of mono- and disubstituted hydrazines may be of importance regarding the carcinogenic properties of these derivatives