Rabbit heart mitochondrial function and nitric oxide metabolism during ischemia-reperfusion

BOMBICINO SS; ZAOBORNYJ T; DONATO M; D’ANNUNZIO V; GELPI R; BOVERIS A,; VALDEZ LB

Santiago, Chile

Congreso; Free Radicals and Antioxidants in Chile 2009: VI Meeting of the Society for Free Radical Biology and Medicine, South American Group; 2009

Society for Free Radical Biology and Medicine, South American Group

The aim was to study left ventricle mitochondrial function, with special attention to NO metabolism, of rabbit heart exposed to ex vivo ischemia-reperfusion. Hearts were removed and perfused according to Landendorff technique. After 15 min of stabilization (0/0), ischemia was induced for 15 min (15/0), followed by 5 or 30 min of reperfusion (15/5 and 15/30). Tissue slice O2 consumption rates were 10% lower after ischemia and 20% lower after 5 and 30 min reperfusion. Ischemia and 5 min of reperfusion decreased state 3 respiration and increased state 4 respiration with malate/glutamate, impairing the RC from 5 to 3.5. These effects were not observed with succinate, suggesting that ischemia-reperfusion damages complex I proteins. For complex I activity, a decrease of 30% was observed after 15 min of ischemia, and the decline was irreversible with 5 or 30 min of reperfusion. Complex II and IV activities were 15 and 30% lower at 15 min of ischemia, but the effect was reversed by 5 and 30 min of reperfusion. Mitochondrial NO production decreased 40% in 15/0 hearts and 75% in 15/5 hearts. After 30 min of reperfusion mtNOS activity was enhanced, reaching values 45% lower than 0/0 hearts. These results are in accordance with mtNOS functional activity measured through O2 consumption, in the presence of L-arginine or L-NMMA: 85% (0/0), 54% (15/0), 8% (15/5) and 23% (15/30). Endogenous mitochondrial NO and NO-derived species are involved in the bioenergetic regulation observed during ischemia and the impairment of mitochondrial function detected after reperfusion.