Changes in brain and plasma amino acids of mice intoxicated with methyl isocyanate

Precolumn derivatization with OPA was used for the analysis of brain and plasma free amino acids of mice after the administration of different doses (0.25 LD50, 0.5 LD50 and LD50) of methyl isocyanate (MIC) for different durations (45 min, 4 h, 4 days and 7 days). In general, there were a dose-dependent decrease in brain free amino acid content with the exception of glycine and arginine (increased above the control level with 0.25 LD50 and 0.5 LD50 doses), and taurine which increased with 0.5 LD50 and LD50 doses in 45 min. All the amino acids from plasma were increased with all the three doses, with the exception of arginine which decreased at the 0.25 LD50 dose in 45 min. With increase in duration of observation to 4 h, 4 days and 7 days, the brain amino acid content was still below the control levels and plasma levels were higher as compared to the respective controls. The only exceptions were serine, histidine, alanine and arginine, which decreased on the 7th day. This study suggests that MIC produced an imbalance of both the brain and plasma amino acids, suggesting neurotoxic and systemic effects.