Portal de Periódicos da CAPES

Mitochondrial functions under hypoxic conditions: The steady states of cytochrome c reduction and of energy metabolism

1974; Elsevier BV; Volume: 347; Issue: 3 Linguagem: Inglês

10.1016/0005-2728(74)90074-7

1879-2650

Tukasa Sugano, Nozomu Oshino, Britton Chance,

Electrochemical sensors and biosensors

1. The effect of low oxygen concentration on the oxidation-reduction states of cytochrome c and of pyridine nucleotide, on Ca2+ uptake, on the energy-linked reduction of pyridine nucleotide by succinate, and on the rate of oxygen consumption have been examined under various metabolic conditions, using pigeon heart mitochondria. 2. The oxygen concentration required to provide half-maximal reduction of cytochrome c (p50c) ranges from 0.27 to 0.03 μM (0.2-0.02 Torr) depending upon the metabolic activity. There is a linear increase of the p50c value with increasing respiratory rate. 3. The fraction of the normoxic respiration that is observed at p50c is 70–90% under State 4 conditions, but is 30% under State 3 conditions. 4. The oxygen requirement for half-maximal reduction of pyridine nucleotide (p50PN) varies less than p50c, being 0.08 μM in State 3 and 0.06 μM in the uncoupled state. 5. The ability of the mitochondria to exhibit an energy-linked reduction of pyridine nucleotide by succinate disappears at an oxygen concentration of 0.09 μM (0.06 Torr). Below this oxygen concentration, endogenous Ca2+ begins to be released from the mitochondria. Thus, the critical oxygen concentration for bioenergetic function of mitochondria corresponds approximately to 50% reduction of pyridine nucleotide (p50PN).