STANDARDIZATION OF ACID-HYDROLYSIS PROCEDURE FOR URINARY 3-METHYLHISTIDINE DETERMINATION BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

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 determi ne total 3-meH excretion, samples require acid hydrolysis prior to det ermination by high-performance liquid chromatography. This study evalu ated the stability of 3-meH at various times and temperatures of hydro lysis and determined the optimal conditions for hydrolysis of samples. Increasing temperature (120 degrees C) results in significant degrada tion 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 deg rees C for 8 to 12 h is recommended for determining total 3-meH concen trations in rat urine.