[Whole body protein turnover, synthesis and breakdown in patients receiving total parenteral nutrition (TPN) before and after recovery from surgical stress].

Abstract This study was conducted to clarify the mechanisms underlying the loss of body nitrogen after trauma. Six patients who underwent abdominal surgery and six for control were studied. The measurement of whole body protein turnover was made on the third and tenth postoperative day during TPN with constant infusion of [15N] glycine according to Picou and Taylor-Roberts. The measurement was also made on six control patients during TPN in non-stressed state. The rates of whole body protein turnover (Q), synthesis (S) and breakdown (B) were calculated from the plateau 15N enrichment of urinary total N, which was analyzed with a mass spectrometer. The values were compared with control and the changes in the individual patients were examined by a paired t-test. Immediately after operation, Q and B were significantly elevated (p less than 0.05 and p less than 0.02, respectively), and reduced with the improvement of N-balance after recovery from stress by 0.95 +/- 0.21 and 0.61 +/- 0.13 g X protein/kg X day, respectively. The changes in Q and B were statistically significant (p less than 0.005 and p less than 0.005, respectively). Whereas, no tendency of alteration in S was found throughout the study. It is concluded that protein turnover rate increases in surgical stress, and that the increased protein catabolism rather than the alteration in synthesis could account for the postoperative nitrogen losses.