Standardization of acid hydrolysis procedure for urinary 3-methylhistidine determination by high-performance liquid...

The N-acetylated form of N-methylhistidine (3-methylhistidine, 3-meH), a non-invasive marker of proteolysis, accounts for 80-90% of total 3-meH excretion (acetylated+non-acetylated 3-meH) in the rat. To determine total 3-meH excretion, samples require acid hydrolysis prior to determination by high-performance liquid chromatography. This study evaluated the stability of 3-meH at various times and temperatures of hydrolysis and determined the optimal conditions for hydrolysis of samples. Increasing temperature (120 degrees C) results in significant degradation of 3-meH with no appreciable change in concentration being noted at 80 degrees C. Hydrolysis at 100 degrees C for 1.5 to 4 h or 80 degrees C for 8 to 12 h is recommended for determining total 3-meH concentrations in rat urine.