IRON DELOCALIZATION OCCURS DURING ISCHEMIA AND PERSISTS ON REOXYGENATION OF SKELETAL-MUSCLE

Attenuation of oxidative reperfusion injury in skeletal muscle by the administration of iron-chelating compounds suggests that ischemia-repe rfusion Is associated with delocalization of iron with subsequent cata lysis of hydroxyl radical generation. To test this hypothesis we exami ned the extent of iron liberation and lipid peroxidation In a well-est ablished model of high-grade partial hindlimb ischemia and reperfusion . Laparotomy was performed on heparinized male Sprague-Dawley rats wit h Isolation of the infrarenal aorta. Resting membrane potential (E(m)) and conjugated diene content in hindlimb skeletal muscle were determi ned along with plasma iron concentration and percent saturation of tra nsferrin in five groups of animals. Baseline animals (n = 6) underwent a 30-minute postoperative stabilization period before data collection ; Sham ischemia animals (n = 10) underwent aortic exposure without cla mping for 120 minutes; ischemia animals (n = 8) underwent aortic clamp ing for 120 minutes; sham reperfusion animals (n = 8) undervent aortic exposure without clamping for 150 minutes; reperfusion animals (n = 8 ) underwent aortic clamping for 120 minutes followed by 30 minutes of reperfusion. Iron delocalization occurred during ischemia, as indicate d by a significant rise in percent saturation of transferrin over that of the corresponding sham group (35% +/- 2% vs 25% +/- 2%; p < 0.05) and persisted during reperfusion (39% +/- 5% vs 27% +/- 3%; p <0.05). Depolarization of resting E(m) was noted during ischemia (-75.7 +/- 1. 7 mV vs -92.6 +/- 0.4 mV in the corresponding sham group; p < 0.01), w ith only partial repolarization demonstrated after reperfusion (-82.2 +/- 1.7 mV; p < 0.01 vs all other groups). Reperfusion was also associ ated with a significant increase in skeletal muscle content of conjuga ted dienes (p < 0.05 vs all other groups). These data indicate that ir on delocalization occurs during skeletal muscle ischemia and reperfusi on and is associated with significant membrane dysfunction and postisc hemic lipid peroxidation. A role for iron in the catalysis of free rad ical-mediated oxidative reperfusion injury in skeletal muscle is stron gly supported.