Staples 2010 Abstract IOC60

Staples JF, Chung DJ, Armstrong C (2010) Fast in, slow out: Kinetics of mitochondrial metabolic suppression during hibernation entrance and arousal. MiPNet15.10.

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Staples JF, James F, Chung DJ, Armstrong C (2010)

Event: IOC60

During entrance into a torpor bout the whole-animal metabolic rate of mammalian hibernators can decrease by up to 100-fold within a matter of hours. This metabolic suppression corresponds with a rapid decrease in succinate-fuelled State 3 respiration rates of liver mitochondria, measured at 37 °C. When isolated from 13-lined ground squirrel (Ictodomys tridecemlineatus) in early entrance (Tb=30 °C), respiration decreased by 61% compared with interbout euthermia. Respiration did not decline further in late entrance (Tb=15 °C) or steady-state torpor (Tb=5 °C). In contrast, during early arousal (Tb=15 °C), despite rapid increases in metabolic rate, State 3 respiration did not increase significantly from torpor levels. By the time Tb reached 30 °C in late arousal, however, respiration was 3-fold higher than torpor and continued to increase gradually, so that in interbout euthermia it was 6-fold higher than torpor and not significantly different from the summer active state. Preincubation with 2 mM isocitrate (removing oxaloacetate inhibition of succinate dehydrogenase) increased respiration only in torpor and early arousal. The “fast” initiation of mitochondrial metabolic suppression during entrance and its “slow” reversal during arousal suggests a mechanism that requires fairly high body temperatures.

• Keywords: Hibernation, Mitochondria, Ictidomys, Ground squirrel

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Organism: Other mammals  Tissue;cell: Liver  Preparation: Isolated mitochondria  Enzyme: Complex II;succinate dehydrogenase  Regulation: Temperature