Bioenergetic regulation of nitric oxide production in rat mitochondria

VALDEZ LB; ZAOBORNYJ T; BOMBICINO SS; BOVERIS A

Dublin, Irlanda

Congreso; 15th European Bioenergetics Conference; 2008

European Bioenergetics Society

Not only heart mitochondrial membranes (2.08±0.08 nmol/min.mg protein), but also heart coupled mitochondria, exhibit an enzymatic production of NO. MtNOS activity is 40% lower in state 3 than in state 4, and shows an exponential dependence on membrane potential. The aim of this work was to further characterize mtNOS activity regulation by the redox state of the respiratory chain and membrane potential. The generation of NO (nmol/min.mg protein) by heart submitochondrial particles resulted 0.45±0.02. This value was enhanced up to 0.81±0.09 when mtNOS activity was assessed in the presence of succinate and ATP. The addition of rotenone inhibited by 50% this reversed electron transfer-supported mtNOS activity. Besides, the ability of mtNOS to modulate O2 uptake and H2O2 production, is termed mtNOS functional activity. Supplementation of state 3 mitochondria with L-arginine decreased respiration rates by 15-20%, while addition of L-NAME increased O2 consumption by 10%. The addition of L-arginine enhanced state 4 H2O2 production by 14-21%, whereas supplementation with L-NAME declined H2O2 generation by 7-9%. Interestingly, these effects were observed in coupled mitochondria, but not in mitochondrial membranes. We conclude through direct and indirect evidence, that mtNOS activity is regulated by membrane potential; and that respiratory chain electron flow modulates NO production; in agreement with the reported physical interaction of mtNOS and respiratory chain components.