Generation of peroxynitrite contributes to ischemia-reperfusion injury in isolated rat hearts.
OBJECTIVE
The acute release of radicals upon reperfusion following myocardial ischemia may include both nitric oxide (NO) and superoxide anion (O2-.). The generation of peroxynitrite (ONOO-) from these radicals may contribute to ischemia-reperfusion injury. Our objective was to measure the generation of ONOO- during reperfusion of isolated hearts subjected to ischemia and to determine the effects of inhibition of NO synthase with NG-monomethyl-L-arginine (L-NMMA), or supplementation of NO with S-nitroso-N-acetyl-D,L-penicillamine (SNAP), on ONOO- generation and on the recovery of mechanical function.


RESULTS
Isolated rat hearts were perfused at constant pressure with Krebs' buffer containing L-tyrosine, which reacts with ONOO- to form dityrosine, a fluorescent product. Dityrosine was detected in the coronary effluent of hearts infused with synthetic ONOO-. In hearts subjected to 20 min of global, no-flow ischemia there was a marked rise in endogenous ONOO- formation which peaked at 30 s of reperfusion. Formation of ONOO- was dependent upon synthesis of both NO and O2-., as dityrosine release was abolished by L-NMMA or superoxide dismutase, respectively. L-NMMA caused a concentration-dependent improvement in the recovery of mechanical function during reperfusion. Infusion of SNAP also abolished dityrosine release at reperfusion and improved the recovery of post-ischemic function.


CONCLUSIONS
Our results show for the first time that reperfusion of the ischemic heart causes the acute production of ONOO-. Inhibiting the biosynthesis of ONOO- with L-NMMA or antagonizing its oxidant actions with SNAP are possible strategies to protect the heart from ischemia-reperfusion injury.
Yasmin
W
W
Department of Pediatrics, University of Alberta, Edmonton, Canada.
Strynadka
K D
KD
Schulz
R
R
D000818:Animals; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000517:prevention & control; D009206:Myocardium / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D026423:S-Nitroso-N-Acetylpenicillamine; D014665:Vasodilator Agents / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000494:pharmacology*
D009566:Nitrates; D014665:Vasodilator Agents; C039642:peroxynitric acid; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D019001:Nitric Oxide Synthase; D010396:Penicillamine