Dependence of the mitochondrial adaptive capacity of hepatocytes on the oxidative substrates availability

Abstract

The ability of the mitochondria to compensate for energy expenditure of cells largely depends on the availability of the oxidative substrates, transported across the intact plasma membrane with molecular carriers of limited affinity. The aim of this study was to investigate the dependence of adaptive respiratory responses of mitochondria of intact hepatocytes on the oxidative substrates. Basal and FCCP-stimulated respiration rates were determined with Clark electrode. After 15-minute incubation in the medium with the oxidative substrates or their combinations (glutamine, pyruvate, succinate, monomethyl succinate, α-ketoglutarate, dimethyl-α-ketoglutarate (2 mM) or glucose (10 mM)), isolated hepatocytes were added into the respiratory chamber. FCCP concentration was 0.25, 0.5 and 1 μM. The adaptive capacity of mitochondria was characterized by the maximal uncoupled respiration rate (the highest respiration rate among all tested FCCP concentrations), the optimal FCCP concentration (the concentration at which the maximal rate is achieved) and the area under the curve (AUC) of the dependence of the uncoupled respiration rate on FCCP concentration. The adaptive capacity of mitochondria, evaluated by AUC, increases in this order of substrates: glucose (0.063 r.u.), endogenous substrates (0.067 r.u.), glutamine (0.092 r.u.), pyruvate (0.113 r.u.), α-ketoglutarate (0.113 r.u.), succinate (0.152 r.u.), dimethyl-α -ketoglutarate (0.156 r.u.), and monomethyl succinate (0.172 r.u.). The adaptive capacity of mitochondria of hepatocytes seems to be partly dependent on plasma membrane transporters affinities (Km) to the oxidative substrates. The presence of glucose in the medium does not improve the adaptive capacity of hepatic mitochondria.

Keywords

• tive capacity of mitochondria
• fccp
• hepatocytes
• oxidative substrates