METHYLATION OF NEURONAL AND GLIAL MACROMOLECULES BY METHYLNITROSOUREA AND DIMETHYLNITROSAMINE INVIVO

Rats were injected i.p. with radioactive methylnitrosourea and dimethyl-nitrosamine and neuronal and glial cell fractions separated from brain tissue after 4 h, 72 h and 10 days. DNA, RNA and protein were purified and specific radioactivity was determined. At all labelling times with methylnitrosourea neuronal nucleic acids were methylated to higher (1.5-2.0:1) specific radio-activity than glial nucleic acids. 7-Methylguanine appeared to be the major purine adduct and O6-methylguanine a minor adduct in the two cell fractions. The proportion of O6-methylguanine was equal in the two cell fractions. With dimethylnitrosamine, glial macromolecules were methylated to a greater extent than neuronal macromolecules. Neuronal cells appear to be inactive in the metabolism of dimethylnitrosamine. The level of methylation in brain tissue by dimethylnitrosamine was of a lower order than in liver tissue. © 1979.