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First published online March 16, 2007
Journal of Experimental Biology 210, 1216-1224 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.002881
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Maximum cardiac performance and adrenergic sensitivity of the sea bass Dicentrarchus labrax at high temperatures
1 UBC Centre for Aquaculture and the Environment, Faculty of Agricultural
Sciences and Department of Zoology, 2357 Main Mall, University of British
Columbia, Vancouver, BC, V6T 1Z4, Canada
2 Göteborg University, Department of Zoology, PO Box 463, SE-405 30,
Göteborg, Sweden
3 University of Linköping, Department of Biology, IFM, SE-581 83,
Linköping, Sweden
4 Institut des Sciences de l'Evolution, Département de Biologie
Intégrative, 1 Quai de la Daurade, 34200 Sète, France
* Author for correspondence (e-mail: farrellt{at}interchange.ubc.ca)
Accepted 6 February 2007
We examined maximum cardiac performance of sea bass Dicentrarchus labrax acclimated to 18°C and 22°C, temperatures near the optimum for growth of this species. Our aim was to study whether cardiac performance, especially the effect of adrenergic stimulation, differed when compared to salmonids. Sea bass and salmonids are both athletic swimmers but their cardiac anatomy differs markedly. The sea bass ventricle does not receive any oxygenated blood via a coronary circulation while salmonids have a well-developed arterial supply of oxygen to the compact layer of the ventricle. Using in situ perfused heart preparations, maximum cardiac performance of 18°C-acclimated sea bass (i.e. cardiac output=90.8± 6.6 ml min–1 kg–1 and power output=11.41±0.83 mW g–1) was found to be comparable to that previously reported for rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta at similar temperatures and with tonic adrenergic (5 nmol l–1 adrenaline) stimulation. For 22°C-acclimated sea bass, heart rate was significantly higher, but maximum stroke volume was reduced by 22% (1.05±0.05 ml kg–1) compared with 18°C (1.38± 0.11 ml kg–1). As a result, maximum cardiac output (99.4±3.9 ml min–1 kg–1) was not significantly different at 22°C. Instead, maximum power output was 27% higher at 22°C (14.95±0.96 mW g–1) compared with 18°C, primarily because of the smaller relative ventricular mass in 22°C-acclimated sea bass. Compared with tonic adrenergic stimulation with 5 nmol l–1 adrenaline, maximum adrenergic stimulation of the sea bass heart produced only modest stimulatory effects at both temperatures (12–13% and 14–15% increases in maximum cardiac output and power output, respectively, with no chronotropic effect). Adrenergic stimulation also increased the cardiac sensitivity to filling pressure, with the maximum left-shift in the Starling curve being produced by 50–100 nmol l–1 adrenaline at 18°C and 10–50 nmol l–1 adrenaline at 22°C. We show that the sea bass, which lacks a coronary arterial oxygen supply to the ventricle, has a powerful heart. Its maximum performance is comparable to a salmonid heart, as is the modest stimulatory effect of adrenaline at high temperature.
Key words: sea bass, heart, cardiac output, heart rate, temperature, adrenaline
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