Quantification of N(τ) -Methylhistidine and N(π)-Methylhistidine in Chicken Plasma by Liquid Chromatography–Tandem Mass Spectrometry

The concentration of N(τ)-methylhistidine in plasma provides an index of skeletal muscle protein breakdown. This study aimed to establish a quantitative method for measuring the concentrations of N(τ)-methylhistidine and its isomer N(π)-methylhistidine in chicken plasma, using liquid chromatography–tandem mass spectrometry with stable isotope dilution analysis. The acceptable linear ranges of detection were 1.56–50.00 μmol/L for N(τ)-methylhistidine and 0.78–25.00 μmol/L for N(π)-methylhistidine. The proposed method detected changes in the plasma levels of N(τ)-methylhistidine and N(π)-methylhistidine in response to fasting and re-feeding. These results suggest that the method developed in this study can be used for the simultaneous measurement of N(τ)-methylhistidine and N(π)-methylhistidine in chicken plasma.