Glutathione reverses endothelial damage from peroxynitrite, the byproduct of nitric oxide degradation, in crystalloid cardioplegia

Background-NO has been advocated as an adjunct to cardioplegia solutions. H owever, NO undergoes a rapid biradical reaction with superoxide anions to p roduce peroxynitrite (ONOO-). ONOO- in crystalloid cardioplegia solution in duces injury to coronary endothelium and to systolic function after cardiop legia and reperfusion. However, ONOO- may be degraded to less lethal or car dioprotective intermediates with glutathione (GSH) in reactions separate fr om its well known antioxidant effects. We hypothesized that GSH detoxifies ONOO- and reverses defects in endothelial function and systolic function wh en present in crystalloid cardioplegia. Methods and Results-In anesthetized dogs on cardiopulmonary bypass, a 45-mi nute Period of global normothermic ischemia was followed by 60 minutes of i ntermittent cold crystalloid cardioplegia (Plegisol) and 3 hours of reperfu sion. The cardioplegia solution contained 5 mu mol/L authentic ONOO-; catal ase was included to attenuate the potential antioxidant effects of GSH and to unmask the effects on ONOO-. In 1 group (CP+GSH, n=5), the cardioplegia contained 500 mu mol/L GSH, whereas 1 group received crystalloid cardiopleg ia without CSII (CCP, n=6). There were no group differences in postcardiopl egia left ventricular systolic function (end-systolic pressure-volume relat ion, impedance catheter: CCP 10.0+/-2.4 versus CP+GSH 10.6+/-1.3 mmHg/mL) o r diastolic chamber stiffness (beta -coefficient. CCP 0.35+/-0.2 versus CPGSH 0.31+/-0.18). Myocardial neutrophil accumulation (myeloperoxidase activ ity) was attenuated in CP+GSH versus CCP (2.2+/-0.7 versus 5.4+/-1.2, P<0.0 5). In postexperimental coronary arteries, maximal endothelium-dependent re laxation was greater in CP+GSH than in CCP (118+/-6% versus 92+/-5%, P<0.05 ), with a smaller EC,, value (-7.10+/-0.05 versus -6.98+/-0.03, respectivel y, P<0.05). Smooth muscle relaxation was complete in both groups. The adher ence of neutrophils to postexperimental coronary arteries as a measure of e ndothelial function was less in CP+GSH than in CCP (98+/-18 versus 234+/-36 neutrophils/mm(2), P<0.05). Nitrosoglutathione, a byproduct of the reactio n between ONOO- and GSH, was greater in CP+GSH than in CCP (4.1+/-2.3 versu s 0.4+/-0.2 mug/mL, P<0.05). Conclusions-GSH in crystalloid cardioplegia detoxifies ONOO- and forms card ioprotective nitrosoglutathione, resulting; in attenuated neutrophil adhere nce and selective endothelial protection through the inhibition of neutroph il-mediated damage.