Alterations in enterocyte mitochondrial respiratory function and enzyme activities in gastrointestinal dysfunction following brain injury

AIM: To determine the alterations in rat enterocyte mitochondrial respiratory function and enzyme activities following traumatic brain injury (TBI). METHODS: Fifty-six male SD rats were randomly divided into seven groups (8 rats in each group): a control group (rats with sham operation) and traumatic brain injury groups at 6, 12, 24 h, days 2, 3, and 7 after operation. TBI models were induced by Feendy' s free-falling method. Mitochondrial respiratory function (respiratory control ratio and ADP/O ratio) was measured with a Clark oxygen electrode. The activities of respiratory chain complex I-IV and related enzymes were determined by spectrophotometry. RESULTS: Compared with the control group, the mitochondrial respiratory control ratio (RCR) declined at 6 h and remained at a low level until day 7 after TBI (control, 5.42 +/- 0.46; 6 h, 5.20 +/- 0.18; 12 h, 4.55 +/- 0.35; 24 h, 3.75 +/- 0.22; 2 d, 4.12 +/- 0.53; 3 d, 3.45 +/- 0.41; 7 d, 5.23 +/- 0.24, P < 0.01). The value of phosphate-to-oxygen (P/O) significantly decreased at 12, 24 h, day 2 and day 3, respectively (12 h, 3.30 +/- 0.10; 24 h, 2.61 +/- 0.21; 2 d, 2.95 +/- 0.18; 3 d, 2.76 +/- 0.09, P < 0.01) compared with the control group (3.46 +/- 0.12). Two troughs of mitochondrial respiratory function were seen at 24 h and day 3 after TBI. The activities of mitochondrial complex. (6 h: 110 +/- 10, 12 h: 115 +/- 12, 24 h: 85 +/- 9, day 2: 80 +/- 15, day 3: 65 +/- 16, P < 0.01) and complex. (6 h: 105 +/- 8, 12 h: 110 +/- 92, 24 h: 80 +/- 10, day 2: 76 +/- 8, day 3: 68 +/- 12, P < 0.01) were increased at 6 h and 12 h following TBI, and then significantly decreased at 24 h, day 2 and day 3, respectively. However, there were no differences in complex. and. activities between the control and TBI groups. Furthermore, pyruvate dehydrogenase (PDH) activity was significantly decreased at 6 h and continued up to 7 d after TBI compared with the control group (6 h: 90 +/- 8, 12 h: 85 +/- 10, 24 h: 65 +/- 12, day 2: 60 +/- 9, day 3: 55 +/- 6, day 7: 88 +/- 11, P < 0.01). The changes in alpha-ketoglutaric dehydrogenase (KGDH) activity were similar to PDH, except that the decrease in KGDH activity began at 12 h after TBI (12 h: 90 +/- 12, 24 h: 80 +/- 9, day 2: 76 +/- 15, day 3: 68 +/- 7, day 7: 90 +/- 13, P < 0.01). No significant change in malate dehydrogenase (MDH) activity was observed. CONCLUSION: Rat enterocyte mitochondrial respiratory function and enzyme activities are inhibited following TBI. Mitochondrial dysfunction may play an important role in TBI-induced gastrointestinal dysfunction. (C) 2014 Baishideng Publishing Group Inc. All rights reserved.