Formation of N-nitrosoiminodialkanoic acids and their unsuitability as biological monitors for endogenous nitrosation of dipeptides.

Nitrosation of dipeptides that do not contain imino amino acids leads to rearrangement and formation of N-nitrosoiminodialkanoic acids. The optimal pH is 2.0 (0.8-3.2% yield). Under normal gastric conditions, a maximum yield of 0.1 mumol total N-nitrosoiminodialkanoic acid would be obtained for a typical dietary intake of 0.1 mol dipeptide. This corresponds to a total concentration of about 20 micrograms N-nitrosoiminodialkanoic acid/l gastric juice over a 24-h period. N-Nitrosoiminodialkanoic acids are excreted quantitatively in urine when fed by gavage to rats; however, they were not detected in normal human urine. It was concluded that determination of these compounds in human urine is not a suitable method for monitoring endogenous nitrosation of dipeptides.