Inhibition of peroxynitrite precursors, NO and O2, at the onset of reperfusion improves myocardial recovery

Aim of study: Previous reports note an increase in both reactive oxygen species (ROS) and nitric oxide ((NO)-N-center dot) at the onset of myocardial reperfusion. We tested the hypothesis that inhibition of (NO)-N-center dot or ROS production at the time of reperfusion improves recovery of post-ischemic myocardial function. Methods and materials: Isolated rat hearts were perfused with temperature controlled (37.4 degrees C) modified Krebs Henseleit buffer solution at 85mm Hg. Following 20min of global ischemia, hearts were reperfused for the first 10min with: (1) standard buffer (control), (2) buffer with a NOS inhibitor, N-nitro-L-arginine methyl ester (L-NAME), (3) buffer with superoxide dismutase (SOD) or (4) buffer with N-morpholinosydnonimine hydrochloride (SIN-1), a peroxynitrite generator. Tissue 02 and (NO)-N-center dot were continuously measured with thin electrochemical probes embedded in the watt of the LV. ROS was measured with the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) (40 mM). LV contractile function was continuously monitored. Results: Recovery of LV contractile function was significantly improved in hearts initially reperfused with L-NAME and SOD and significantly depressed in hearts reperfused with SIN-1 compared with control (p < 0.01, n = 5-8 per group). DMPO-adduct during reperfusion (measure of ROS) was significantly decreased with SOD (p < 0.001 versus L-NAME and Control, n = 4 per group) and unchanged with L-NAME and SIN-1 compared with Control. With L-NAME, tissue No-center dot and PO2 were significantly decreased, independent of coronary flow, during reperfusion compared with control and SIN-1. Conclusions: Inhibition Of O2(center dot-) or (NO)-N-center dot at the time of reperfusion improves early reperfusion LV function and alters tissue oxygen tension. In contrast to pre-ischemic treatments, intervention to reduce peroxynitrite generation at the onset of reperfusion can effectively improve post-ischemic myocardial recovery. (c) 2007 Elsevier Ireland Ltd. All rights reserved.