Nitric oxide is produced through mitochondrial reverse electron transfer.

BOMBICINO SS; IGLESIAS DE; ZAOBORNYJ T; BOVERIS A; VALDEZ LB

Dresden

Congreso; 10th European Biophysics Congress - EBSA 2015; 2015

European Biophysical Societies´Association (EBSA)

Heart phosphorylating electron transfer particles (ETPH) showed a NAD+ reductase activity of 63.9±3.3 nmol/min.mg protein, sustained by reverse electron transfer at expenses of ATP and succinate. This activity was inhibited by rotenone (99%), oligomycin (98%) and m-CCCP (93%). ETPH produced NO at 1.1 ± 0.1 nmol/min.mg protein. In the presence of the compounds needed to carry out the reverse electron flow, ETPH produced 0.96 ± 0.07 nmol NO/min.mg protein, suggesting that NO production can be supported by electrons derived from the respiratory chain. Rotenone completely inhibited mtNOS activity supported by reverse electron transfer measured in ETPH, but that inhibitor did not reduce the activity of isolated nNOS, indicating that the inhibitory effect of rotenone on NO production by ETPH is due to an electron flow blockage and not to a direct action on NOS structure. A mitochondrial fraction enriched in complex I produced 1.72 ± 0.18 nmol NO/min.mg protein and reacted with anti-nNOS antibodies, suggesting that complex I physically and functionally interacts with the NOS enzyme. These data show that mitochondrial NO production is supported by reverse electron flow of the respiratory chain, this latter a phenomenon that could occur in physiopathological conditions.