SUPEROXIDE ANION PRODUCTION BY LEUKOCYTES EXPOSED TO POSTISCHEMIC SKELETAL-MUSCLE

Superoxide anion (O2-) and polvmorphonuclear leukocytes (PMNs) have be en implicated in the genesis of skeletal muscle ischemia-reperfusion ( I-R) injury, but the source of (O2-) has not been established. We stud ied PMNs as a potential source of O2- using a ferricytochrome reductio n 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 contra lateral 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 samp les were also obtained prior to surgical preparation and after reperfu sion. Assays for O2- were performed with and without zymosan (Z) activ ation. Results are expressed as nmol O2-/2 x 10(6) PMNs +/- SEM. Basel ine production of O2- was 0.49 +/- 0.54 in central venous samples; Z i ncreased the values to 6.77 +/- 2.13. After 2 hrs of reperfusion, cent ral O2- was 1.57 +/- 0.75, which increased to 7.1 +/- 1.04 with Z. Gra cilis venous samples O2- values with and without Z are reported in Tab le I. One way measures of analysis of variance showed no significant ( p > 0.05) differences between samples. Our results demonstrate that PM Ns are not the sole source of O2- in the pathophysiology of skeletal m uscle I-R injury. PMN associated injury may be mediated by mechanisms other than O2- production.