Mitochondrial function and nitric oxide metabolism in heart ischemia-reperfusion

VALDEZ LB

Buenos Aires, Argentina

Workshop; Workshop “Oxidative stress and antioxidants"; 2009

catedra de Fisicoquímica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires.

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 17% and 41% lower after 5 and 30 min reperfusion. Ischemia and 30 min of reperfusion decreased state 3 respiration (18%) when malate/glutamate were used as substrates, impairing the RC from 5.4 to 4.7. These effects were not observed with succinate, suggesting that ischemia-reperfusion damages complex I proteins. For complex I-III activity, a decrease of 18% was observed after 15 min of ischemia, and the decline was irreversible with 5 or 30 min of reperfusion. Complex II-III and IV activities were 16% lower at 15 min of ischemia, but this effect was reversed by 5 and 30 min of reperfusion. The pattern observed for complex I activity was observed for mtNOS activity as well: mitochondrial NO production decreased 30% in 15/0 hearts and the activity remained reduced in 15/5 hearts. These results are in accordance with mtNOS functional activity measured through O2 consumption, using malate/glutamate, in the presence of L-arginine or L-NMMA: 58% (0/0), 37% (15/0), 23% (15/5) and 34% (15/30). In addition, 30 min reperfusion produced a 3-fold increase in tyrosine nitration of mitochondrial proteins. These data suggest that endogenous mitochondrial NO and NO-derived species (ONOO-) are involved in the bioenergetic regulation observed during ischemia and the impairment of mitochondrial function detected after reperfusion.