Effects of magnesium and nucleotides on the proton conductance of rat skeletal-muscle mitochondria

Cadenas, Susana; Brand, Martin D.

doi:10.1042/bj3480209

Cited by 41 publications

(16 citation statements)

References 26 publications

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“…The results from the present study are in agreement with the former studies: during hibernation, state 4 respiration was decreased by 41% in mitochondria isolated from liver and assayed at 37°C (Table 1). Procedural differences may account for the discrepancy between our and previous (28) studies: magnesium inhibits succinate dehydrogenase in rat liver (26,29) and skeletal muscle (15) mitochondria, and the inclusion of magnesium in the assay buffer (28) may have masked differences in state 4 respiration between hibernating and active animals. This possibility is supported by the finding that the average state 4 respiration of both active and hibernating liver mitochondria in goldenmantled ground squirrels (28) was less than that measured in hibernators in this study and in Richardson's ground squirrels (30).…”

Section: Discussioncontrasting

confidence: 69%

Tissue-specific depression of mitochondrial proton leak and substrate oxidation in hibernating arctic ground squirrels

Barger

Brand

Barnes

et al. 2003

American Journal of Physiology-Regulatory, Integrative and Comp

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A significant proportion of standard metabolic rate is devoted to driving mitochondrial proton leak, and this futile cycle may be a site of metabolic control during hibernation. To determine if the proton leak pathway is decreased during metabolic depression related to hibernation, mitochondria were isolated from liver and skeletal muscle of nonhibernating (active) and hibernating arctic ground squirrels (Spermophilus parryii). At an assay temperature of 37 degrees C, state 3 and state 4 respiration rates and state 4 membrane potential were significantly depressed in liver mitochondria isolated from hibernators. In contrast, state 3 and state 4 respiration rates and membrane potentials were unchanged during hibernation in skeletal muscle mitochondria. The decrease in oxygen consumption of liver mitochondria was achieved by reduced activity of the set of reactions generating the proton gradient but not by a lowered proton permeability. These results suggest that mitochondrial proton conductance is unchanged during hibernation and that the reduced metabolism in hibernators is a partial consequence of tissue-specific depression of substrate oxidation.

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Section: Discussioncontrasting

confidence: 69%

Tissue-specific depression of mitochondrial proton leak and substrate oxidation in hibernating arctic ground squirrels

Barger

Brand

Barnes

et al. 2003

American Journal of Physiology-Regulatory, Integrative and Comp

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“…The kinetics of the mitochondrial proton leak were measured by determining the dependence of the respiration rate required to drive proton leak (in the presence of oligomycin to inhibit ATP synthesis) on mitochondrial membrane potential. It was measured using an electrode sensitive to the potential‐sensitive probe, TPMP (triphenylmethylphosphonium), in the presence of nigericin to dissipate the pH gradient (Brand 1995, Cadenas & Brand, 2000). Intact mitochondria extracted from the thoraces of 11 day‐old flies were resuspended at 0.2–0.3 mg of protein per mL in assay medium containing oligomycin (1 µg mL −1 ), nigericin (100 ng mL −1 ) and rotenone (5 µ m ).…”

Section: Methodsmentioning

confidence: 99%

Sex differences in survival and mitochondrial bioenergetics during aging inDrosophila

et al. 2007

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SummaryThe goal of this study is to test the role of mitochondria and of mitochondrial metabolism in determining the processes that influence aging of female and male Drosophila . We observe that Drosophila simulans females tended to have shorter lifespan, higher levels of hydrogen peroxide production and significantly lower levels of catalase but not superoxide dismutase compared to males. In contrast, mammalian females tend to be longer lived, have lower rates of reactive oxygen species production and higher antioxidant activity. In both Drosophila and mammals, mitochondria extracted from females consume a higher quantity of oxygen when provided with adenosine diphosphate and have a greater mtDNA copy number than males. Combined, these data illustrate important similarities between the parameters that influence aging and mitochondrial metabolism in Drosophila and in mammals but also show surprising differences.

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“…Thus, the kinetic response of the proton conductance pathway to its driving force (membrane potential, Dw) can be measured as the relationship between respiration rate and mitochondrial Dw when the latter is varied by titrating the electron transport system (ETS) with inhibitors (Cadenas and Brand 2000). Mitochondria were isolated from diapause and postdiapause embryos of A. franciscana (Kwast and Hand 1993;Reynolds and Hand 2004), and the dependence of proton leak respiration on mitochondrial Dw was measured based on methods previously described (Brand 1995;Brand et al 2005;Affourtit et al 2012).…”

Section: Kinetics Of Mitochondrial Proton Leakmentioning

confidence: 99%

Metabolic Downregulation and Inhibition of Carbohydrate Catabolism during Diapause in Embryos ofArtemia franciscana

Patil

Marden²,

Brand³

et al. 2013

Physiological and Biochemical Zoology

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Diapause embryos were collected from ovigerous females of Artemia franciscana at the Great Salt Lake, Utah, and were synchronized to within 4 h of release. Respiration rate for these freshly released embryos across a subsequent 26-d time course showed a rapid decrease during the first several days followed thereafter by a much slower decline. The overall metabolic depression was estimated to be greater than 99%. However, proton conductance of mitochondria isolated from diapause and postdiapause embryos was identical. Because proton leak is apparently not downregulated during diapause, mitochondrial membrane potential is likely compromised because of the very low metabolic rate observed for diapause embryos. Given that trehalose is the primary fuel used by these embryos, we measured metabolic intermediates along the catabolic pathway from trehalose to acetyl-CoA for both diapause and postdiapause (active) embryos in order to identify sites of metabolic inhibition. Comparison of product-to-substrate ratios for sequential enzymatic steps revealed inhibition during diapause at trehalase, hexokinase, pyruvate kinase, and pyruvate dehydrogenase. Measurements of ATP, ADP, and AMP allowed calculations of substantial decreases in ATP:ADP ratio and in adenylate energy charge during diapause. The phosphorylation of site 1 for pyruvate dehydrogenase (PDH) subunit E1α was higher in diapause embryos than in postdiapause embryos, which is consistent with PDH inhibition during diapause. Taken together, our findings indicate that restricted substrate availability to mitochondria for oxidative phosphorylation contributes to downregulating metabolic rate during diapause.

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Effects of magnesium and nucleotides on the proton conductance of rat skeletal-muscle mitochondria

Cited by 41 publications

References 26 publications

Tissue-specific depression of mitochondrial proton leak and substrate oxidation in hibernating arctic ground squirrels

Tissue-specific depression of mitochondrial proton leak and substrate oxidation in hibernating arctic ground squirrels

Sex differences in survival and mitochondrial bioenergetics during aging inDrosophila

Metabolic Downregulation and Inhibition of Carbohydrate Catabolism during Diapause in Embryos ofArtemia franciscana

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