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Mitochondria are major sources of reactive oxygen species (ROS), which play important roles in both physiological and pathological processes. However, the specific contributions of different ROS production and scavenging components in the mitochondria of metabolically active tissues such as heart and kidney cortex and outer medulla (OM) are not well understood. Therefore, the goal of this study was to determine contributions of different ROS production and scavenging components and provide detailed comparisons of mitochondrial respiration, bioenergetics, ROS emission between the heart and kidney cortex and OM using tissues obtained from the same Sprague-Dawley rat under identical conditions and perturbations. Specifically, data were obtained using both NADH-linked substrate pyruvate + malate and FADH2-linked substrate succinate followed by additions of inhibitors of different components of the electron transport chain (ETC) and oxidative phosphorylation (OxPhos) and other ROS production and scavenging systems. Currently, there is limited data available for the mitochondria of kidney cortex and OM, the two major energy-consuming tissues in the body only next to the heart, and scarce quantitative information on the interplay between mitochondrial ROS production and scavenging systems in the three tissues. The findings from this study demonstrate significant differences in mitochondrial respiratory and bioenergetic functions and ROS emission among the three tissues. The results quantify the rates of ROS production from different complexes of the ETC, identify the complexes responsible for variations in mitochondrial membrane depolarization and regulations of ROS production, and quantify the contributions of ROS scavenging enzymes towards overall mitochondrial ROS emission. These findings advance our fundamental knowledge of tissue-specific and substrate-dependent mitochondrial respiratory and bioenergetic functions and ROS emission. This is important given the critical role that excess ROS production, oxidative stress, and mitochondrial dysfunction in the heart and kidney cortex and OM play in the pathogenesis of cardiovascular and renal diseases, including salt-sensitive hypertension. Keywords: Forward and reverse electron transfer; Mitochondrial metabolism; NADPH oxidase; Oxidative stress; ROS emission; ROS production and scavenging; Respiration and bioenergetics.
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This content will become publicly available on August 1, 2026
Evolutionary diversity of muscle OXPHOS efficiency in vitro across ectothermic vertebrates
Oxidative metabolism meets the majority of vertebrate energy demands through the coupling of mitochondrial respiration to ATP production (OXPHOS). In endotherms, variations in OXPHOS coupling efficiency influence metabolic thermogenesis, locomotor economy and reactive oxygen species (ROS) generation. However, the extent of these variations and their functional implications in ectotherms are less clear. We measured mitochondrial oxygen consumption, ATP production and ROS production in permeabilized skeletal muscle fibres from salamanders, frogs and lizards representing ectotherm clades with low, medium and high standard metabolic rates (SMRs), respectively. Consistent with predicted associations with SMR, lizards had the highest capacities for muscle mitochondrial ATP production, while salamanders had the lowest. Unexpectedly, corresponding rates of oxygen consumption followed an opposite trend, reflecting 8.5-fold variations in OXPHOS coupling efficiency between salamanders (the lowest) and lizards (the highest). Intrinsic proton permeability of the inner mitochondrial membrane was the primary source of OXPHOS coupling variation across species, being highest in salamanders and lowest in lizards. Basal proton leak mediated by uncoupling proteins and the adenine nucleotide translocase was only seen in lizards, where it limits mitochondrial ROS production. We infer that diverse evolutionary selection pressures drive unexpectedly wide variations in muscle OXPHOS efficiency with different functional implications across ectotherm clades.
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- Award ID(s):
- 1911585
- PAR ID:
- 10644213
- Publisher / Repository:
- The Royal Society Publishing
- Date Published:
- Journal Name:
- Proceedings of the Royal Society B: Biological Sciences
- Volume:
- 292
- Issue:
- 2053
- ISSN:
- 1471-2954
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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