Urinary excretion of 3-methylhistidine in patients receiving parenteral nutrition.

In an attempt to investigate the kinetics of the muscle protein during parenteral nutrition (PN) and surgical stress, the urinary output of 3-methylhistidine (3-Mehis) was measured in patients receiving PN, then the validity of urinary 3-Mehis excretion as an index for the patient's status of protein nutrition was examined. The amounts of 3-Mehis excreted in 24 hr urine in the 19 healthy males and 10 healthy females were 74.8 +/- 17.1 mg/day and 46.3 +/- 12.4 mg/day, respectively. The changes of daily urinary 3-Mehis output in 6 cases receiving PN for more than 4 weeks were also examined. The average urinary 3-Mehis excretion increased gradually during the course of PN, and by the third week was nearly twice as high as the level before PN. In a further study the influence of surgery upon the urinary excretion of 3-Mehis was examined in 9 patients. Finally, a comparison was made of the nutritional status before and 4 wks after PN in the 6 patients without surgical stress. Urinary 3-Mehis was found to be a good index of both the status of protein nutrition and the fluctuation of muscle protein catabolism.