© 1988 Oxford University Press
research-article |
Role of formaldehyde hydrazone and catalase in hydrazine-induced methylation of DNA guanine
Department of Community and Environmental Medicine, University of California Irvine
1University of California Southern Occupational Health Center Irvine, CA 92717, USA
2To whom reprint requests should be sent
Hydrazine is acutely neurotoxic, hepatotoxic and nephrotoxic; It is also carcinogenic to liver and lung In rodents. Administration of hydrazine results in formation of 7-methylguanine and O6-methylguanine in target organ DNA of rats, mice, hamsters and guinea-pigs. It has been suggested that hydrazine reacts with endogenous formaldehyde to form a condensation product which could be metabolized to a methylating agent. Solutions of 0.51 mM hydrazine and formaldehyde have, upon mixing, NMR spectra (300 MHz) consistent with the formation of formaldehyde hydrazone but not other possible condensation products such as tetraformyltriazine or for-maldehyde azine. These same solutions evidencing hydrazone formation, when incubated in an in vitro system containing post-mitochondrial (S9), microsomal, cytosolic or mitochondrial cell fractions, resulted in the methylatlon of DNA guanine; S9 was the most active fraction. Neither the P-450 monooxygenase nor flavin monooxygenase systems appeared to be important in hydrazine/formaldehyde-induced methylation of DNA. However, sodium azide, cyanamide and carbon monoxide all inhibited S9-supported DNA methylation. Bovine liver catalase, a heme-containing cytochrome, readily transformed hydrazine/formaldehyde to a methylating agent. The data support formation of formaldehyde hydrazone as the condensation product of hydrazine and formaldehyde which is rapidly transformed in various liver cell fractions, perhaps by catalase and/or catalase-like enzymes, to a methylating agent.