Article

Oxidation of succinate in heart, brain, and kidney mitochondria in hypobaria and hypoxia.

Environmental physiology & biochemistry 02/1975; 5(3):189-200.
Source: PubMed

ABSTRACT Exposure of rats to hypobaric stress for periods of up to 36 h caused a consistent change in the succinate-NT reductase activity of the heart mitochondria whereas there was no significant change in the activities of either succinate dehydrogenase and succinate-NT reductase of the brain and the kidney. Mitochondrial succinate dehydrogenase of the heart, the brain and the kidney was activated 2- to 7-fold with the substrate and malonate. The activations obtained with oxalate, citrate and dinitrophenol were relatively lower in comparison to succinate and malonate. Benzohydroquinone and 2-nitrophenol had no stimulatory effect on the heart, the brain and the kidney mitochondria. THE ACTIVATIONS OBTAINED WITH THE VARIOUS EFFECTORS PARTIALLY (OR COMPLETELY IN THE CASE OF SUCCINATE) REVERSED ON WASHING THE MITOCHONDRIAL SAMPLES WITH THE SUCROSE HOMOGENIZING MEDIUM. The effect of ubiquinol, which also activated the enzyme, was only partially reversed after the second preincubation with succinate in the brain and the kidney whereas in the heart the activity was fully reversed. The increased activity of succinate dehydrogenase obtained with ATP and ADP was further enhanced by Mg2+ exclusively in the brain mitochondria, suggesting the possibility of Mg2+-AIP complex as the active species. Succinate-NT reductase of the heart, the brain and the kidney mitochondria showed a high activation with ubiquinone whereas its reduced form had no stimulatory effect.

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    • "A recording electrode solution containing 0 [ATP] was used to dialyse ATP from the cytosol as described elsewhere (Muller et al. 2002). To test the effect of succinate dehydrogenase (SDH) inhibition on NMDAR currents, malonate (5 mm) was bulk perfused (Sivaramakrishnan & Ramasarma, 1975). The potassium ionophore valinomycin (5 μm) and dinitrophenol (DNP; 10 mm) were used as positive controls for uncoupling experiments in isolated mitochondria (Knowles, 1982). "
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