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dc.contributor.authorHickey, Anthony J. R.en_US
dc.contributor.authorRenshaw, Gillianen_US
dc.contributor.authorSpeers-Roesch, Benen_US
dc.contributor.authorRichards, Jeffrey G.en_US
dc.contributor.authorWang, Yuxiangen_US
dc.contributor.authorFarrell, Anthony P.en_US
dc.contributor.authorBrauner, Colin J.en_US
dc.description.abstractHypoxia 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 34 C, 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.en_US
dc.relation.ispartofjournalJournal of Comparative Physiology Ben_US
dc.subject.fieldofresearchMedical Biochemistry and Metabolomics not elsewhere classifieden_US
dc.titleA radical approach to beating hypoxia: depressed free radical release from heart fibres of the hypoxia-tolerant epaulette shark (Hemiscyllum ocellatum)en_US
dc.typeJournal articleen_US
dc.type.descriptionC1 - Peer Reviewed (HERDC)en_US
dc.type.codeC - Journal Articlesen_US
gro.hasfulltextNo Full Text

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