N-TAU-METHYLHISTIDINE IN HUMAN SKELETAL AND SMOOTH-MUSCLE PROTEINS

1. Fifteen pieces of rectus abdominus muscle and fifteen pieces of taenia muscle were removed from patients undergoing various surgical procedures. 2. The muscles were extracted, hydrolysed and the content of Nτ-methylhistidine was measured. 3. The rectus muscles contained 3.13±0.7 μmols Nτ-methylhistidine/g fat-free dry solid andthe taenia muscles 2.4±0.6 μmols/g fat-free dry solid. There was a statistically significant difference (P < 0.05) between these values using the Student's unpaired t test, although this could have been due to contamination of the taenia muscles with connective tissue. 4. The muscle content of Nτ-methylhistidine was at least 40% higher than the only other reported value and therefore the method of calculating muscle protein breakdown based on Nτ-methylhistidine excretion requires revision. © 1979, The Nutrition Society. All rights reserved.