Oxygen free radicals affect cardiac and skeletal cell membrane potential during hemorrhagic shock in rats

Oxygen free radical (OFR) damage of excitable cell membranes (heart and skeletal muscle) during hemorrhagic shock and after resuscitation was studied in control rats and in rats pretreated with superoxide dismutase (SOD) and catalase (CAT; 6,000 U each) before hemorrhage. Their mean arterial pressure (MAP) was lowered to and maintained at 45 mmHg until 30% of the shed blood was spontaneously reinfused. The remaining blood and twice that volume of lactated Ringer solution were then infused. Cardiac output and organ blood flow were measured by the microsphere technique. The resting membrane potential (Em) and tissue ATP content in the heart and skeletal muscle were determined. There was no significant difference between the control and SOD + CAT groups in shock duration, maximal shed blood, hemodynamics, regional blood flow, or in ATP content in both heart and skeletal muscle, both during shock and after resuscitation. Radical scavenger treatment did not prevent muscle depolarization during shock. After resuscitation, however, significant repolarization in hearts and skeletal muscle of the SOD + CAT group (heart, -70.0 +/- 1.1; muscle, -87.0 +/- 0.6 mV) was noted when compared with the controls (heart, -62.5 +/- 1.2; muscle, -82.7 +/- 1.1 mV; P less than 0.05). This implicates OFRs as mediators of excitable cell membrane injury following resuscitation.