Influence of temperature on calcium sensitivity in the ventricular myocardium of the South American lungfish: Effects of extracellular calcium and adrenaline |
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| Institution: | 1. Centre for Research on Exercise, Physical Activity and Health, School of Human Movement and Nutrition Sciences, The University of Queensland, Australia;2. Health and Exercise Science, Flinders University, South Australia, Australia;3. Recreation, Exercise, and Sport Science Department, Western State Colorado University, Gunnison, CO, United States;4. Institut des Sciences du Sport de l''Universite de Lausanne (ISSUL), Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland |
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| Abstract: | The mechanical properties of ventricular myocardium of the South American lungfish, Lepidosiren paradoxa, acclimated to 25 °C, were evaluated in vitro at 15, 25 and 35 °C. The inotropism (Fc—% of initial values) of ventricle strips was examined in response to adrenaline (from 10−8 to 10−5 M) and extracellular calcium (from 2.5 to 14.5 mM) in all experimental temperatures. At 15 and 25 °C, Fc rose when extracellular Ca2+ or adrenaline were increased, while Fc remained unchanged at 35 °C. These results suggest that at lower temperatures Ca2+ availability is a limiting step to cardiac performance and can be ameliorated by adrenergic stimulation. In contrast, since inotropic agents failed to increase cardiac inotropism at 35 °C, lungfish myocytes seem to show a high temperature sensitivity, which increases Ca2+-buffering capacity and/or Ca2+ transportation from and to cytosol as well as myofilaments Ca2+ sensitivity. |
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