Mitochondrial Sensitivity to Adp in Permeabilized Fibers Changed As A Function of Cardiac Muscle Compartments: Left/Right Atria and Ventricles of Sheep Heart

Because of the balance between ATP supply and ATP demand, alterations in cardiac energetics potentially affect cardiac work and may explain pathologies. Neverthelesss energetics alterations in each compartment remain unknown. Since mitochondrial oxidative phosphorylation is the main process of energy supply, mitochondrial sensitivity to energetic intermediates (e.g. ADP) is here investigated in a compartment‐specific way.KmADP were obtained in sheep permeabilized fibers of right and left ventricles and atria using O2 consumption measurements (OROBOROS Oxygraph‐2k), carried out in Mir05 with glutamate (5 mM) and malate (2 mM), at 25°C.Basal respiration (V0) and maximal ADP‐stimulated respiration (Vmax) were similar among atria or ventricles (meanV0 = 33 ± 3.9 and meanVmax = 72 pmol.sec−1.mg−1 dry wt). Interestingly, KmADP were significantly higher in atria, especially in right one, than in ventricles, that were consequently characterized by a 1.5 to 3‐fold higher sensitivity to ADP compared to left and right atria.In beating heart, for a given energy state of the cell, mitochondria are more responsive in ventricles than in atria and more responsive in the left than in the right atrium. Interestingly mitochondrial responsiveness is likely in adequation with requested work in each chamber of the healthy heart and may be closely related to the ventricle ability to withstand problems of arrhythmias.