A radical approach to beating hypoxia: depressed free radical release from heart fibres of the hypoxia-tolerant epaulette shark (Hemiscyllum ocellatum)

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Title A radical approach to beating hypoxia: depressed free radical release from heart fibres of the hypoxia-tolerant epaulette shark (Hemiscyllum ocellatum)
Author Hickey, Anthony J. R.; Renshaw, Gillian Mary Claire; Speers-Roesch, Ben; Richards, Jeffrey G.; Wang, Yuxiang; Farrell, Anthony P.; Brauner, Colin J.
Journal Name Journal of Comparative Physiology B
Year Published 2012
Place of publication Germany
Publisher Springer
Abstract Hypoxia and warm ischemia are primary concerns in ischemic heart disease and transplant and trauma. Hypoxia impacts tissue ATP supply and can induce mitochondrial dysfunction that elevates reactive species release. The epaulette shark, Hemiscyllum ocellatum, is remarkably tolerant of severe hypoxia at temperatures up to 34C, and therefore provides a valuable model to study warm hypoxia tolerance. Mitochondrial function was tested in saponin permeabilised ventricle fibres using high-resolution respirometry coupled with purpose-built fluorospectrometers. Ventricular mitochondrial function, stability and reactive species production of the epaulette shark was compared with that of the hypoxia-sensitive shovelnose ray, Aptychotrema rostrata. Fibres were prepared from each species acclimated to normoxic water conditions, or following a 2 h, acute hypoxic exposure at levels representing 40% of each species’ critical oxygen tension. Although mitochondrial respiratory fluxes for normoxia-acclimated animals were similar for both species, reactive species production in the epaulette shark was approximately half that of the shovelnose ray under normoxic conditions, even when normalised to tissue oxidative phosphorylation flux. The hypoxia-sensitive shovelnose ray halved oxidative phosphorylation flux and cytochrome c oxidase flux was depressed by 34% following hypoxic stress. In contrast, oxidative phosphorylation flux of the epaulette shark ventricular fibres isolated from acute hypoxia exposed the animals remained similar to those from normoxia-acclimated animals. However, uncoupling of respiration revealed depressed electron transport systems in both species following hypoxia exposure. Overall, the epaulette shark ventricular mitochondria showed greater oxidative phosphorylation stability and lower reactive species outputs with hypoxic exposure, and this may protect cardiac bioenergetic function in hypoxic tropical waters.
Peer Reviewed Yes
Published Yes
Alternative URI http://dx.doi.org/10.1007/s00360-011-0599-6
Volume 182
Issue Number 1
Page from 91
Page to 100
ISSN 0174-1578
Date Accessioned 2012-08-07
Language en_US
Research Centre Griffith Health Institute; Heart Foundation Research Centre
Faculty Griffith Health Faculty
Subject Medical Biochemistry and Metabolomics
URI http://hdl.handle.net/10072/47513
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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