title: Effects of fatty acid provision during severe hypoxia on routine and maximal performance of the in situ tilapia heart.
abstract: The ability to maintain stable cardiac function during environmental hypoxia exposure is crucial for hypoxia tolerance in animals and depends upon the maintenance of cardiac energy balance as well as the state of the heart's extracellular environment (e.g., availability of metabolic fuels). Hypoxic depression of plasma [non-esterified fatty acids] (NEFA), an important cardiac aerobic fuel, is a common response in many species of hypoxia-tolerant fishes, including tilapia. We tested the hypothesis that decreased plasma [NEFA] is important for maintaining stable cardiac function during and following hypoxia exposure, based on the premise that continued reliance upon cardiac fatty acid metabolism under such conditions could impair cardiac function. We examined the effect of severe hypoxia exposure (PO2 < 0.2 kPa) on routine and maximum performance of the in situ perfused tilapia heart under conditions of routine (400 μmol L(-1)) and low (75 μmol L(-1)) [palmitate], which mimicked the in vivo levels of plasma [NEFA] found in normoxic and hypoxic tilapia, respectively. Under both concentrations of palmitate, the in situ tilapia heart showed exceptional hypoxic performance as a result of a high maximum glycolytic potential, confirming our previous results using a perfusate without fatty acids. We additionally provide evidence suggesting that non-contractile ATP demand is depressed in tilapia heart during hypoxia exposure. Cardiac performance during and following severe hypoxia exposure was unaffected by the level of palmitate. Thus, we conclude that hypoxic depression of plasma [NEFA] in fishes does not play a role in cardiac hypoxia tolerance.
authors.affiliation: Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC V6T 1Z4, Canada. bensr@zoology.ubc.ca
authors.forename: Ben
authors.initials: B
authors.lastname: Speers-Roesch
authors.forename: Sabine L
authors.initials: SL
authors.lastname: Lague
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Farrell
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Richards
mesh_terms: D000818:Animals; D002302:Cardiac Output / Q000502:physiology; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005260:Female; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D000860:Hypoxia / Q000378:metabolism*; D066298:In Vitro Techniques; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology; D019308:Palmitic Acid / Q000494:pharmacology; D010477:Perfusion; D017210:Tilapia / Q000502:physiology*
chemical_list: D005230:Fatty Acids, Nonesterified; D019308:Palmitic Acid; D019344:Lactic Acid; D010100:Oxygen
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