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ABSTRACT The metabolic rate (ṀO2) of eurythermal fishes changes in response to temperature, yet it is unclear how changes in mitochondrial function contribute to changes in ṀO2. We hypothesized that ṀO2 would increase with acclimation temperature in the threespine stickleback (Gasterosteus aculeatus) in parallel with metabolic remodeling at the cellular level but that changes in metabolism in some tissues, such as liver, would contribute more to changes in ṀO2 than others. Threespine stickleback were acclimated to 5, 12 and 20°C for 7 to 21 weeks. At each temperature, standard and maximum metabolic rate (SMR and MMR, respectively), and absolute aerobic scope (AAS) were quantified, along with mitochondrial respiration rates in liver, oxidative skeletal and cardiac muscles, and the maximal activity of citrate synthase (CS) and lactate dehydrogenase (LDH) in liver, and oxidative and glycolytic skeletal muscles. SMR, MMR and AAS increased with acclimation temperature, along with rates of mitochondrial phosphorylating respiration in all tissues. Low SMR and MMR at 5°C were associated with low or undetectable rates of mitochondrial complex II activity and a greater reliance on complex I activity in liver, oxidative skeletal muscle and heart. SMR was positively correlated with cytochrome c oxidase (CCO) activity in liver and oxidative muscle, but not mitochondrial proton leak, whereas MMR was positively correlated with CCO activity in liver. Overall, the results suggest that changes in ṀO2 in response to temperature are driven by changes in some aspects of mitochondrial function in some, but not all, tissues of threespine stickleback.
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Mitochondrial respiration capacity impacts gill tissue regeneration in Atlantic salmon
ABSTRACT Gill regeneration in fish varies inter- and intra-specifically. The latter may be associated with myriad factors including capacity of energy metabolism. This study investigated whether mitochondrial respiration capacity influences the degree of gill regeneration and features of mitochondria in regenerated tissue by feeding fish an experimental diet aimed at modulating mitochondrial efficiency. Atlantic salmon reared on standard and experimental diet were subjected to 50% filament resection on a subset of filaments on the ventral and dorsal regions of the first gill arch. Mitochondrial respiration and citrate synthase activity (CSA) were measured in the resected tips of filaments (week-0) and then in the regenerated tissue at 20 weeks post-resection (week-20). The degree of filament regeneration was measured at week-20. The experimental diet reduced CSA and respiratory control ratio (RCR), and increased proton leak at week-0, which was associated with a 30% reduction in tissue regeneration compared with fish on standard diet. While CSA increased in the regenerated tissue of experimental diet fish, there was a decline in other metrics of mitochondrial respiration including state 3, proton leak and RCR irrespective of diet. Overall, mitochondrial respiration efficiency at week-0 was positively correlated with the degree of subsequent gill tissue regeneration. Additionally, state 3 respiration and proton leak at week-20 were positively correlated with tissue regeneration, whereas CSA exhibited a negative relationship. Our results indicate that the capacity of mitochondrial respiration may at least partially explain the inter-individual variation in tissue regeneration, but mitochondrial function in the regenerating tissue may be limited.
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- Award ID(s):
- 2305837
- PAR ID:
- 10630783
- Publisher / Repository:
- Company of Biologists
- Date Published:
- Journal Name:
- Journal of Experimental Biology
- Volume:
- 228
- Issue:
- 7
- ISSN:
- 0022-0949
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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