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).

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 7after 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 complexⅠ-Ⅳand 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 at12,24 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 Ⅰ (6 h:110±10,12 h:115±12,24 h:85±9,day 2:80±15,day 3:65±16,P<0.01)and complexⅡ(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 day3,respectively.However,there were no differences in complex Ⅰ andⅡactivities 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 inα-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,day7:90±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.