title: Mitochondrial metabolism in hibernation: metabolic suppression, temperature effects, and substrate preferences.
abstract: We compared liver and skeletal muscle mitochondrial function among activity states to characterize regulated reversible metabolic suppression in the mammalian hibernator Spermophilus tridecemlineatus. At 37 degrees C, succinate oxidation was 70% lower in the liver mitochondria from torpid animals than in those from summer-active animals or in animals arousing from torpor. Respiration was very sensitive to temperature (Q(10) 5.8-9.8), and when measured at 25 degrees or 5 degrees C there was no difference among the three states. Liver mitochondria from summer-active animals oxidized pyruvate and beta -hydroxybutyrate at higher rates than those from torpid animals, and flux through complex 4 of the electron transport chain was about three- and fivefold higher than flux through complexes 2-4 and complexes 1-4, respectively. In the hibernating and arousing animals there was no difference in flux through complexes 2-4 and complex 4, suggesting a downregulation of cytochrome c oxidase in liver mitochondria during the hibernation season. Muscle mitochondrial respiration did not differ between the torpid and summer-active states in any of the parameters measured. The data support a regulated, reversible decrease of liver (but not muscle) mitochondrial oxidative phosphorylation in hibernating ground squirrels.
authors.affiliation: Department of Biology, University of Western Ontario, London, Canada.
authors.forename: Helen M
authors.initials: HM
authors.lastname: Muleme
authors.forename: Amy C
authors.initials: AC
authors.lastname: Walpole
authors.forename: James F
authors.initials: JF
authors.lastname: Staples
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000378:metabolism; D000818:Animals; D001831:Body Temperature / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D006605:Hibernation / Q000502:physiology*; D008930:Mitochondria, Liver / Q000378:metabolism*; D008931:Mitochondria, Muscle / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D019289:Pyruvic Acid / Q000378:metabolism; D012589:Sciuridae / Q000378:metabolism* / Q000502:physiology; D019802:Succinic Acid / Q000378:metabolism; D013686:Telemetry / Q000662:veterinary
chemical_list: D018698:Glutamic Acid; D019289:Pyruvic Acid; D019802:Succinic Acid; D020155:3-Hydroxybutyric Acid