Cardioprotective Effects of Red Blood Cells on Ischemia and Reperfusion Injury in Isolated Rat Heart: Release of Nitric Oxide as a Potential Mechanism
AbstractBackground : Circulating cells influence myocardial function during ischemia and reperfusion. (eg, neutrophils exacerbate, and platelets protect the myocardium from deterioration). This study was designed to determine the role of red blood cells on myocardial function following ischemia and reperfusion in isolated rat hearts. Methods and Results : Exposure of buffer-perfused hearts to 40 minutes of total ischemia followed by 30 minutes of reperfusion resulted in myocardial dysfunction and injury, indicated by decrease in the force of cardiac contraction (FCC, −25 ± 4%). increase in the coronary perfusion pressure (CPP, +20 ± 3%) and decrease in myocardial superoxide dismutase (SOD, 2.5 ± 0.2 vs 3.5 ± 0.4 U/mg protein in sham ischemic hearts, P < .05). Perfusion of the hearts with washed rat red blood cells showed significant protective effects against ischemia and reperfusion, indicated by minimal change in FCC (-10 ± 4%) and CPP (+3 ± 3%) (both P < .01 vs buffer alone perfused hearts) and preservation of myocardial SOD activity (2.8 ± 0.4 U/mg protein, P < .05 vs buffer alone perfused hearts). The cardioprotective effects of red blood cells were attenuated when the red blood cells were preincubated with the nitric oxide synthase inhibitors N w -nitro-L-arginine (L-NNA, 5 times 10 -4 M) or N w -nitro-L-arginine methyl ester (L-NAME, 5 times 10 -1 M) at 37°C for 60 minutes before perfusion of the heart. Perfusion of hearts with the nitric oxide precursor L-arginine (2 times 10 -4 M) also exerted significant protective effects on FCC (-14 ± 4%). CPP (+12 ± 3%) and myocardial SOD activity (2.9 ± 0.2 U/mg protein) following ischemia and reperfusion. In other studies, washed rat red blood cells expressed nitric oxide synthetase activity which was inhibited by both l-NNA and L-NAME. Conclusions : These results suggest that red blood cells exert cardioprotective effects against ischemia and reperfusion at least in part by the L-arginine-nitric oxide pathway in isolated rat hearts.