Superoxide anion production by leukocytes exposed to post-ischemic skeletal muscle.

Superoxide anion (O2-) and polymorphonuclear leukocytes (PMNs) have been implicated in the genesis of skeletal muscle ischemia-reperfusion (I-R) injury, but the source of (O2-) has not been established. We studied PMNs as a potential source of O2- using a ferricytochrome reduction assay in 5 anesthetized dogs. Using a gracilis muscle model of I-R, 6 hours of ischemia was followed by 2 hours of reperfusion. The contralateral muscle served as control. Prior to ischemia and after 0.5 and 2.0 hours of reperfusion, PMNs were separated from the gracilis venous effluent of ischemic (I) and control (C) muscles. Central venous samples were also obtained prior to surgical preparation and after reperfusion. Assays for O2- were performed with and without zymosan (Z) activation. Results are expressed as nmol O2-/2 x 10(6) PMNs +/- SEM. Baseline production of O2- was 0.49 +/- 0.54 in central venous samples; Z increased the values to 6.77 +/- 2.13. After 2 hrs of reperfusion, central O2- was 1.57 +/- 0.75, which increased to 7.1 +/- 1.04 with Z. Gracilis venous samples O2- values with and without Z are reported in Table I. One way measures of analysis of variance showed no significant (p > 0.05) differences between samples. Our results demonstrate that PMNs are not the sole source of O2- in the pathophysiology of skeletal muscle I-R injury. PMN associated injury may be mediated by mechanisms other than O2- production.