The value and limitation of iloprost infusion in decreasing skeletal muscle necrosis

Glycine preserves function and decreases necrosis in skeletal muscle undergoing ischemia and reperfusion injury

BACKGROUND

Glycine (GLY) is a neutral amino acid that has been shown to be cytoprotective in the kidneys of dogs and rabbits undergoing ischemia-reperfusion injury. To investigate whether GLY exhibits a protective effect on skeletal muscle subjected to ischemia and reperfusion injury, we used a well-described gracilis muscle model in canines.

METHODS

Twelve adult mongrel dogs were subjected to 6 hours of ischemia in 1 randomly selected side. The dogs were randomized into 2 groups: group 1 (6 animals) underwent 15 minutes of perfusion with 2.2% GLY, and group 2 (6 animals) underwent 15 minutes of perfusion with normal saline solution (NS) only. Both groups had normothermic reperfusion for 1 hour along with the corresponding perfusate. Muscle biopsy specimens were taken, frozen in liquid nitrogen, and stored at -70 degrees C. Muscle injury was evaluated at 48 hours by measuring weight gain (edema), maximal contractile force, and percent of muscle necrosis. Adenosine triphosphate (ATP) and phosphocreatine (Pcr) (an energy store for ATP synthesis) levels were determined by using high performance liquid chromatography.

RESULTS

In group 1, the average weight gain was 57% +/- 11.27% while in group 2 it was 100% +/- 12.48%. Maximal muscle contractile force was 712.5 +/- 68 g for group 1 and 511 +/- 27.91 g for group 2. The amount of muscle necrosis was 30 +/- 3.7% in group 1, as opposed to 63 +/- 10% in group 2. The ATP content was 0.07 +/- 0.03 nmol/mg wet tissue weight (post-ischemia with NS) and 0.21 +/- 0.08 nmol/mg wet tissue weight (post-ischemia with GLY). Pcr content was 0.19 +/- 0.04 mmol/mg wet tissue weight (post-ischemia with NS) and 0.27 +/- 0.04 micromol/mg wet tissue (post-ischemia and infused with GLY) (P <.05).

CONCLUSIONS

These data show that GLY preserves muscle function, decreases edema and the amount of muscle necrosis and preserves energy stores in this canine model. Because GLY can be safely given systemically in human beings in higher concentrations than that given in our model, as it is given in parenteral nutrition, its mechanism of action should be further investigated for its potential use in the clinical setting of ischemia and reperfusion injury.

Experimental models of chronic lower extremity arterial occlusive disease: lessons for drug development

Peripheral vascular disease is the result of chronic vascular insufficiency. As the vascular insufficiency of the lower limbs progressively deteriorates, the condition progresses from intermittent claudication (pain upon exercise) to pain at rest and gangrene. In very severe cases amputation of the leg may be necessary. Whilst dieting, cessation of smoking and physical exercise all beneficially affect the progression of the disorder, the available drug therapy is of limited benefit. Very effective pharmacological agents capable of alleviating the symptoms of chronic peripheral vascular disease have not been developed. In order to mimic the vascular insufficiency of intermittent claudication, an animal model was developed in rats. This involves short-term and long-term 6-10 weeks ligation of the femoral artery of the rat. As demonstrated using measurements of hindlimb skeletal muscle, blood flow, pO2, metabolism and function, a model of intermittent claudication was produced. Using this model, the beneficial effects of physical training was demonstrated. Physical training induced an increase in blood flow and a greater capacity for aerobic metabolism in the partially ischaemic skeletal muscle. The effect of vasodilators has also been examined in this model; in contrast to agents such as Ca2+ antagonists, K+ channel openers appear to improve nutritional blood flow and metabolism in the afflicted skeletal muscle. This model can also be utilized to demonstrate the effects of haemorrheological interventions and of agents modulating muscle metabolism. However, additional effort is required to develop models for the evaluation of efficacy of antiatherothrombotic drugs.

Aspirin increases tissue oedema after skeletal muscle ischaemia and reperfusion

PURPOSE

Skeletal muscle ischaemia reperfusion syndrome affects patients following lower limb revascularisation. Aspirin has the potential to attenuate these effects.

METHODS

Using an established model of hind limb tourniquet ischaemia, the effects of oral and intravenous aspirin administration were observed after 6 h of ischaemia and 18 h reperfusion. Samples were obtained and analysed for muscle viability and oedema, and lung neutrophil infiltration.

RESULTS

Aspirin, when compared to placebo and controls, significantly increased muscle interstitial oedema when given orally and intravenously. It had no effect on tissue viability or lung neutrophil infiltration.

CONCLUSION

Aspirin increases tissue oedema after ischaemia and reperfusion but has no effect on tissue viability. Although its mechanism of action has not been clarified, aspirin may influence the no-reflow component of ischaemia-reperfusion syndrome.