Serving as a reproducible human trauma model, patients (n = 21) undergoing elective cholecystectomy received postoperative total parenteral nutrition with (n = 9) or without (n = 12) alpha-ketoglutarate (AKG) supplementation. Skeletal muscle biopsy specimens were taken before surgery and on the third postoperative day. The postoperative decreases in the concentrations of free glutamine and basic amino acids seen in the control group were counteracted in the AKG group (p less than 0.05). Muscle protein synthesis was estimated by ribosome analysis. On the third postoperative day the control group showed a decline in the polyribosome concentration (25.8% +/- 4.5%; p less than 0.001). No significant change was observed in the AKG group. On each postoperative day the nitrogen balance was negative in the control group but not in the AKG group. In the control group the cumulative nitrogen balance amounted to -9.9 +/- 1.8 gm of nitrogen and in the AKG group -2.6 +/- 2.6 gm of nitrogen, which was significantly different (p less than 0.05). Administration of AKG, the carbon skeleton corresponding to glutamine, produced results similar to those seen when glutamine is added to postoperative total parental nutrition. The results suggest that the availability of precursors for glutamine synthesis in skeletal muscle is crucial for the degree of muscle protein catabolism after surgical trauma.