Flow cytometric analysis of peroxidative activity in granulocytes from coronary and peripheral blood in acute myocardial ischemia and reperfusion in dogs: Protective effect of methionine

Background Methionine has shown protective effects in experimental models o f myocardial infarction and is highly reactive to oxidative compounds produ ced by polymorphonuclear leukocytes (PMN), which in turn have been associat ed with myocardial damage. We have investigated the effect of methionine ad ministration on spontaneous leukocyte peroxidative activity in myocardial i schemia and reperfusion. Methods: In anesthetized dogs, with coronary occlusion (90 min) and reperfu sion (90 min), PMN activation was measured by flow cytometric determination of H2O2 with dihydrorhodamine 123, and correlated to hemodynamic parameter s and infarct presence. To assess a possible direct effect of methionine, H 2O2 and superoxide were measured by flow cytometry in dog leukocyte suspens ions following in vitro stimulation with f-MLP. Results: PMN peroxidative activity in saline-treated dogs increased signifi cantly after coronary occlusion and after reperfusion. These changes were g reater in coronary venous blood than in femoral blood. Methionine administr ation (150 mg/kg, i.v.) before occlusion totally suppressed PMN activation, both after occlusion and reperfusion. Conclusions: PMN are promptly activated in myocardial ischemia, and methion ine administration prevents such activation. However, methionine has no dir ect effect on spontaneous peroxidative activity, and f-MLP induced peroxida tive activity. These in vivo effects of methionine, may additionally contri bute to explain its protective role in experimental myocardial ischemia. Cy tometry 37:140-146, 1999. (C) 1999 Wiley-Liss, Inc.