Exercise in the heat: Effects of dinitrophenol administration

Francesconi, Ralph P.; Hubbard, Richard W.; Matthew, Candace B.; Durkot, M. J.; Bosselaers, M.

doi:10.1016/0306-4565(88)90033-2

Cited by 2 publications

(1 citation statement)

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“…The theoretical maximum, or "mechanistic," ATP/O ratio is based on a fixed stoichiometry for H ϩ and/or ATP/ADP generated or consumed at various steps in OXPHOS. A current mechanistic ATP/O ratio for pyruvate/ malate/succinate-supported OXPHOS can be generated based on the following calculations: 4 H ϩ are pumped from complex I (23), 2 H ϩ from complex III (17), and 4 H ϩ from complex IV (12) per NADH oxidized, yielding 10 H ϩ per NADH. Because FADH 2 from succinate oxidation enters beyond complex I, six H ϩ are pumped per FADH 2 oxidized.…”

Section: Resultsmentioning

confidence: 99%

Direct real-time quantification of mitochondrial oxidative phosphorylation efficiency in permeabilized skeletal muscle myofibers

Lark

Torres

Lin

et al. 2016

American Journal of Physiology-Cell Physiology

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Oxidative phosphorylation (OXPHOS) efficiency, defined as the ATP-to-O ratio, is a critical feature of mitochondrial function that has been implicated in health, aging, and disease. To date, however, the methods to measure ATP/O have primarily relied on indirect approaches or entail parallel rather than simultaneous determination of ATP synthesis and O2 consumption rates. The purpose of this project was to develop and validate an approach to determine the ATP/O ratio in permeabilized fiber bundles (PmFBs) from simultaneous measures of ATP synthesis (JATP) and O2 consumption (JO2 ) rates in real time using a custom-designed apparatus. JO2 was measured via a polarigraphic oxygen sensor and JATP via fluorescence using an enzyme-linked assay system (hexokinase II, glucose-6-phosphate dehydrogenase) linked to NADPH production. Within the dynamic linear range of the assay system, ADP-stimulated increases in steady-state JATP mirrored increases in steady-state JO2 (r(2) = 0.91, P < 0.0001, n = 57 data points). ATP/O ratio was less than one under low rates of respiration (15 μM ADP) but increased to more than two at moderate (200 μM ADP) and maximal (2,000 μM ADP) rates of respiration with an interassay coefficient of variation of 24.03, 16.72, and 11.99%, respectively. Absolute and relative (to mechanistic) ATP/O ratios were lower in PmFBs (2.09 ± 0.251, 84%) compared with isolated mitochondria (2.44 ± 0.124, 98%). ATP/O ratios in PmFBs were not affected by the activity of adenylate kinase or creatine kinase. These findings validate an enzyme-linked respiratory clamp system for measuring OXPHOS efficiency in PmFBs and provide evidence that OXPHOS efficiency increases as energy demand increases.

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Section: Resultsmentioning

confidence: 99%