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Role of N-Methylolpentamethylmelamine in the Metabolic Activation of Hexamethylmelamine¹

Division of Developmental Oncology Research, Department of Oncology, Mayo Clinic, Rochester, Minnesota 55905

² Research Career Development Award CA00755 awarded by the National Cancer Institute, Department of Health and Human Services. To whom requests for reprints should be addressed.

Hexamethylmelamine (HMM) is metabolized by rat hepatic microsomal preparations to reactive species which covalently bind to microsomal protein and to calf thymus DNA added to microsomal incubation mixtures. Covalent binding to macromolecules is dependent on the presence of molecular oxygen and reduced nicotinamide adenine dinucleotide phosphate and is catalyzed by cytochrome P-450 monooxygenases. Reduced nicotinamide adenine dinucleotide-dependent covalent binding of [methyl-¹⁴C]HMM to microsomal protein is greater than that of [ring-¹⁴C]HMM. Reduced nicotinamide adenine dinucleotide phosphate-dependent covalent binding of [ring-¹⁴C]HMM and [methyl-¹⁴C]HMM to calf thymus DNA added to microsomal incubation mixtures are approximately equal. The [ring-¹⁴C]-labeled carbinolamine intermediate in HMM demethylation, N-methylolpentamethylmelamine, covalently binds to microsomal protein and, to a much greater extent, to calf thymus DNA.

¹ This work was supported by Grant CA 30250 awarded by the National Cancer Institute, Department of Health and Human Services.

Received 2/ 7/82. Accepted 11/ 5/82.