The pathophysiological significance of free radicals after reperfusion of ischemic myocardium is still debated. Therefore, experiments were carried out with adultisolated cardiac myocytes in direct contact with stimulated neutrophils (ratio of neutrophils/myocytes: 10/1). Rat cardiac myocytes were isolated byLangendorff - perfusion with collagenase. Three different groups of myocytes were investigated: normoxic, 2h and 12h in anoxic conditions. Neutrophils wereisolated from rat blood by Percoll-gradient-centrifugation. The neutrophils were stimulated with N-formyl Met-Leu-Phe (fMLP), phorbolmyrestatacetate(PMA) and zymosan (Z). The formation of oxygen free radicals was detected as a bioluminescence signal mediated by luminol. The kinetics of the free radicalburst (FRB) resulted in an early maximum for fMLP stimulated neutrophils (20 sec) and for maxima at 5 min (PMA) and 20 min (Z). The FRB was depressedin the presence of normoxic myocytes compraed to controls (neutrophils alone) by 45% (fMLP stimulation), 30% (PMA) and 22% (Z). In contrast the signalincreases in the presence of 2h anoxic myocytes by 12% (fMLP), 81% (PMA) and 6% (Z). In the presence of 12h anoxic myocytes the FRB increases furtherto 918% (fMLP), 576% (PMA) and 198% (Z) compared to controls. Normoxic myocytes are not attacked by activated neutrophils, while the FRB increasesin presence of anoxic myocytes proportional to their ischemic insult. In conclusion, free radicals may be harmful after reoxygenation only to already severelydamaged myocardial cells.
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