Skeletal Muscle Injury In Rats Research Articles

Reduction of reperfusion injury in rat skeletal muscle following administration of cinnamophilin, a novel dual inhibitor of thromboxane synthase and thromboxane A2 receptor.

We used cinnamophilin, a novel dual inhibitor of thromboxane synthase and thromboxane A2 (TXA2) receptor, and superoxide dismutase (SOD) with catalase to examine their protective effect against reperfusion injury in rat skeletal muscle. In 5 groups of 6 wistar rats three hours of ischaemia were induced in one hind limb by application of a tourniquet to the proximal thigh; the contralateral limb served as an internal, nonischaemic control. The first group did not receive any drug nor was it reperfused. In the other four groups, normal saline (reperfusion control), dimethylsulphoxide (DMSO), cinnamophilin, or SOD with catalase was given before removal of the tourniquet and one hour of reperfusion followed. Skeletal muscle injury was measured by a quantitative spectrophotometric assay of triphenyltetrazolium chloride (TTC) reduction and by muscle weight gain. One hour of reperfusion significantly (p<0.05) lowered TTC reduction in ischaemic limbs in the reperfusion control group in comparison with the rats in 3h ischaemia alone. Among the four reperfusion groups, only the cinnamophilin group had significantly lower decrease of TTC reduction and significantly lower muscle weight gain. These results demonstrate the protective effect of cinnamophilin against reperfusion injury of the ischaemic skeletal muscle in rats.

Reduction of skeletal muscle injury through stress conditioning using the heat-shock response.

The heat-shock response refers to specific reversible changes in cellular metabolism that impart a protective effect on individual cells, as well as entire organisms, against subsequent noxious stimuli. Our objective was to quantify skeletal muscle injury following an ischemic event in a rat model by measuring levels of adenosine triphosphate and creatine phosphate. The animals were divided into two experimental groups. Animals in group 1 (n = 15) were subjected to limb ischemia alone, and animals in group 2 (n = 15) were treated with heat-shock conditioning prior to the onset of ischemia. Skeletal muscle specimens also were examined ultrastructurally by electron microscopy. Levels of creatine phosphate were higher in skeletal muscle obtained from animals in group 2. Mean levels of creatine phosphate +/- SEM for groups 1 and 2 were 1.12 +/- 0.06 mumol/gm and 1.95 +/- 0.11 mumol/gm, respectively (p < 0.0001). This represents 18.4 and 31.9 percent of baseline nonischemic levels for groups 1 and 2, respectively (p < 0.0001). Adenosine triphosphate levels were measured in skeletal muscle samples from a subset of animals in each experimental group, group 1 (n = 6) and group 2 (n = 5), and were not significantly different. Electron microscopy demonstrated mitochondrial changes consistent with ischemic injury in group 1, but only nonspecific changes were noted in specimens from group 2. The presence of the primary 72-kDa heat-shock protein (HSP 72) was confirmed only in those animals treated by heat-shock conditioning. We conclude that prior stress conditioning using the heat-shock response confers significant biochemical and ultrastructural protection against ischemic injury in rat skeletal muscle.

Implication of superoxide radicals on ischemia-reperfusion-induced skeletal muscle injury in rats.

This study was designed to clarify the mechanism of ischemia-reperfusion injury to skeletal muscle using long-acting polyoxyethylene-modified superoxide dismutase (SOD-POE) in rats. The gastrocnemius muscles of male Lews rats were investigated. Tissue levels of ATP decreased to 20% of nonischemic values after 3 h ischemia and returned to 94% after 1 h reperfusion. In contrast, they decreased to 3.5% after 4 h ischemia and remained at 20% after 1 h reperfusion. Although SOD-POE did not affect the decrease of ATP during ischemia, it improved significantly the recovery of ATP: 28%. Tissue levels of lipid peroxides (LPO) after 3 h ischemia and 1 h reperfusion did not change significantly compared with the nonischemic levels (0.71 +/- 0.32 nmol/mg protein, mean +/- SD). They showed no increase after 4 h ischemia, but increased explosively after 1 h reperfusion (2.15 +/- 0.73 nmol/mg protein). SOD-POE did not affect LPO levels during ischemia but prevented the increase of LPO significantly after reperfusion (0.98 +/- 0.25 nmol/mg protein). Xanthine oxidase activity did not increase after 3 h ischemia (22.3 +/- 7.0 mU/g) compared with the nonischemic values (17.6 +/- 10.0 mU/g). In contrast, it increased 2.5-fold after 4 h ischemia (50.1 +/- 13.7 mU/g) and remained at a significantly high level after 1 h reperfusion. SOD-POE did not affect xanthine oxidase activity during ischemia and reperfusion. These results suggest that lipid peroxidation by superoxide radicals produced by xanthine oxidase is a contributory factor to ischemia-reperfusion injury to skeletal muscle, and the clinical application of SOD-POE might be expected.

Prediction by 31P‐NMR of the irreversibility of ischemic injury in rat skeletal muscle after ligation of the femoral artery

Rat leg muscles, rendered ischaemic 1 hour previously by ligation of the femoral artery, were submitted to 20 minutes exercise by electrical stimulation of the sciatic nerve. 31P-NMR spectroscopy was used to monitor the changes in high-energy phosphate content of the muscles before, during, and after exercise. Fifteen of the 35 studied muscles evolved toward total necrosis, whereas the others showed signs of recovery over a 2-5-hour postexercise period. Those muscles which did not subsequently recover contained significantly more inorganic phosphate (Pi) at rest (before exercise) than those which recovered. It is suggested that under acute ischaemic conditions the Pi level at rest is correlated with the extent of blood flow restriction and can be used to predict the severity of the ischemia.