Effects of nitric oxide on heart mitochondrial calcium handling

ZAOBORNYJ T; SIVAKUMARAN V; O´ROURKE B

Sierra de la Ventana

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Biofísica; 2014

Sociedad Argentina de Biofísica

Mitochondria provide the cells with both the energy and with the signals that command cell death and survival. Indeed, mitochondria are involved in the production of reactive oxygen species and in Ca2+ handling. The aim of this work was to evaluate heart mitochondrial function, in order to establish the effects of NO and Ca2+ in energy metabolism. Guinea pig heart mitochondria were exposed to NO released from GSNO and SNAP. Mitochondrial NO production, membrane potential and Ca2+ uptake were followed simultaneously using a spectrofluorometer. Isolated mitochondria O2 consumption was assessed using an extracellular flux analyzer. Energized mitochondria were submitted to Ca2+ pulses (10 uM) up to a final concentration of 80-100 uM (200-450 nmol/mg protein), showing no significant alterations in matrix volume and membrane potential. In the presence of NO donors (25 to 100 uM), Ca2+ uptake was slower and extramitochondrial Ca2+ concentration increased. When single 50 uM Ca2+ pulses were added, mitochondria treated with NO donors showed a decreased Ca2+ accumulation rate (40-50%) with an IC50 of about 400 uM (180 nM NO). The addition of L-arginine or NOS inhibitors to control mitochondria produced changes in Ca2+ uptake and in DAF-FM signal. State 4 O2 uptake was not modified by NO. The addition of Ca2+ to the medium produced a 20% enhancement in state 4-O2 consumption and this effect was abolished by NO. These results suggest that Ca2+ and NO act as signals that coordinate cytosolic workload and mitochondrial energy metabolism.