Mitochondrial alterations in skeletal muscle submitted to total ischemia.

BACKGROUND: The role of mitochondrial lesions in the pathogenesis of irreversible cellular ischemia is controversial. The inability to restore mitochondrial function is correlated with the inability to reverse cell damage in various tissues. The objective of the present study was to compare parameters associated with oxidative phosphorylation and the inner mitochondrial membrane potential of skeletal muscle of rats submitted to total ischemia in order to determine which mitochondrial alterations are mainly affected in this condition.
MATERIAL AND METHODS: Wistar rats were submitted to 5 h total ischemia using the tourniquet method (ischemic limb group). The contralateral limb of each rat was used as control (control limb group). After the ischemic period, muscle biopsies were obtained for the isolation of the mitochondrial fractions, which were submitted to polarographic analysis for the determination of ADP-activated oxygen consumption (state 3), basal respiration (state 4), and the ratio of the two respiratory activities: the respiratory control ratio (RCR). The potential of the inner mitochondrial membrane was determined by measuring the fluorescence difference between coupled and uncoupled mitochondria using safranine O as indicator.
RESULTS: After 5 h of ischemia, a significant reduction of all parameters studied was observed in skeletal muscle submitted to ischemia compared to the control limbs.
CONCLUSIONS: Five-hour total ischemia applied to rat skeletal muscle led to the inhibition of the mitochondrial respiratory chain (represented by decreased state 3 and state 4 respiration rates). The percentage decrease in the electrical potential of the inner membrane was similar to the percentage reductions observed for state 4 respiration and the RCR. The parameter mostly affected by ischemia was ADP-activated respiration (state 3).