Surgical trauma decreases glutathione synthetic capacity in human skeletal muscle tissue

Abstract

To gain insight into cellular metabolism underlying the glutathione (GSH) alterations induced by surgical trauma, we assessed postoperative skeletal muscle GSH metabolism and its redox status in 10 patients undergoing elective abdominal surgery. Muscle biopsy specimens were taken from the quadriceps femoris muscle before and at 24 and 72 h after surgery. GSH concentrations decreased by 40% at 24 h postoperatively compared with the paired preoperative values ( P < 0.001) and remained low at 72 h ( P < 0.01). The concentration of GSH disulfide (GSSG) did not significantly change throughout the study period, whereas the total GSH (as GSH equivalent) concentration decreased after surgery. Of the GSH constituent amino acids, the concentration of cysteine remained unchanged throughout the study period (from 28.2 ± 10.1 preoperatively to 29.4 ± 13.9 at 24 h postoperatively and to 28.3 ± 15.6 μmol/kg wet wt at 72 h postoperatively). Despite a reduction in glutamate concentration by 40% 24 h after surgery, no correlation was established between GSH and glutamate concentrations postoperatively. Activity of γ-glutamylcysteine synthetase did not change significantly after surgery, whereas GSH synthetase activity decreased postoperatively (from 66.4 ± 19.1 preoperatively to 41.0 ± 10.5 24 h postoperatively, P < 0.01, and to 46.0 ± 11.7 μU/mg protein 72 h postoperatively, P < 0.05). The decrease of GSH was correlated to the reduced GSH synthetase activity seen at 24 h postoperatively. These results indicate that the skeletal muscle GSH pool is diminished in patients after surgical trauma. The depletion of the GSH pool is associated with a decreased activity of GSH synthetase, indicating a decreased GSH synthetic capacity in skeletal muscle tissue.