Lower-than-normal
tyrosine concentrations of unexplained pathogenesis in plasma and intracellular body water have been reported in patients with
chronic renal failure. We found a derivative of
tyrosine that is not measured by the usual methods of
amino-acid analysis because its alpha-amino group is blocked and cannot react to form other derivatives. An in vivo covalent reaction with
urea-derived
cyanate forms alpha-amino-carbamoyl-
tyrosine (
N-C-Tyr) in patients with
end-stage renal disease. A longitudinal study of patients with
end-stage renal disease who were treated with
continuous ambulatory peritoneal dialysis shows that plasma that is obtained within 4 hours of the morning meal contains 70.1 +/- 6 mumol/L of
tyrosine (mean +/- SEM) and 77.2 +/- 12 mumol/L of
N-C-Tyr (mean +/- SEM). Thus there is a molecule of
N-C-Tyr for each molecule of
tyrosine present. The carbamoylation index or ratio of
N-C-Tyr to
tyrosine, blood
urea nitrogen, episodes of
peritonitis, and changes in dialysis protocol were compared. A reduction in the number of
peritoneal dialysis exchanges resulted in parallel increases in carbamoylation index and blood
urea nitrogen. Altering dialysis by increasing the number of exchanges or adding supplemental
hemodialysis resulted in a decrease in the carbamoylation index with a delayed decrease in blood
urea nitrogen. We found a significant increase of
N-C-Tyr (p = 0.005) and of the carbamoylation index (p = 0.004) during six episodes of
peritonitis compared with 10 periods of no
peritonitis in two patients who had multiple episodes of
peritonitis.(ABSTRACT TRUNCATED AT 250 WORDS)