Nitric oxide is produced through mitochondrial reverse electron transfer.

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

Valencia

Congreso; Annual Meeting of Oxygen Club of California, OCC 2015, World Congress: Oxidants and Antioxidant in Biology; 2015

Oxygen Club of California

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 (RET) 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 NO/min.mg protein by the mtNOS reaction. In conditions of 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 low isopotential components of the respiratory chain. Rotenone completely inhibited NO production 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, indicating that complex I physically and functionally interacts with mtNOS enzyme. These data show that mitochondrial NO production can be supported by reverse electron flow of the respiratory chain, a phenomenon that could occur in physiological and pathological conditions.