Evaluation of genetic risks of alkylating agents IV. Quantitative determination of alkylated amino acids in haemoglobin as a measure of the dose after-treatment of mice with methyl methanesulfonate.

The present study explores the possibilities of using specific amino acids in haemoglobin for tissue dosimetry of alkylating agents. The well-known directly alkylating compound methyl methanesulfonate has been used as a model compound.In one experiment ³H-labelled methyl methanesulfonate was given to mice intraperitoneally at three dose levels. The degree of alkylation of haemoglobin exhibited a linear dependence on the quantity of methyl methanesulfonate injected. The degree of alkylation of guanine-N-7 in DNA indicated a slight positive deviation from linearity at high doses.After a single injection the degree of alkylation of cysteine-S and histidine-N-3 in haemoglobin decreased linearly with time reaching the value zero after about 40 days (the life-time of the erythrocytes in the mouse). This demonstrates a stability of these alkylated products, which is fundamental to their use as integral dose monitors.In a second experiment mice were treated with methyl methanesulfonate once a week over a period of 8 weeks. The experiment demonstrated an accumulation of alkylated groups in haemoglobin in agreement with expectation.A method for the quantitative determination of S-methylcysteine in a protein hydrolysate by gas chromatography was developed.