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Temperature acclimation modifies Na+ current in fish cardiac myocytes
Jaakko Haverinen1, Matti Vornanen
1University of Joensuu, Department of Biology, PO Box 111, 80101 Joensuu, Finland.
The Journal of Experimental Biology
|July 6, 2004
Summary
Temperature acclimation alters fish cardiac sodium current (INa) differently based on species lifestyle. Cold-dormant carp show decreased INa, while cold-active trout exhibit increased INa, impacting cardiac function in cold environments.
Area of Science:
- Cardiovascular physiology
- Comparative physiology
- Environmental adaptation
Background:
- Fish cardiac function is influenced by temperature, requiring physiological adjustments for survival in cold environments.
- Sarcolemmal Na+ current (INa) plays a crucial role in cardiac myocyte electrical activity and impulse propagation.
- Different fish species exhibit varied strategies for coping with cold, including dormancy and active behavior.
Purpose of the Study:
- To investigate how temperature acclimation modifies cardiac sarcolemmal Na+ current (INa) in fish with different cold-survival strategies.
- To test the hypothesis that INa plasticity varies between cold-dormant and cold-active fish species.
- To compare INa characteristics across crucian carp, rainbow trout, and burbot to understand species-specific adaptations.
Main Methods:
- Electrophysiological recordings of Na+ current (INa) in cardiac myocytes from acclimated fish.
- Comparison of INa density and voltage-dependent properties (steady-state activation) between species.
- Analysis of INa charge influx and potential role in excitation-contraction coupling.
Main Results:
- Cold acclimation decreased INa density in cold-dormant crucian carp and increased it in cold-active rainbow trout.
- Trout INa steady-state activation shifted to more negative voltages after cold acclimation, enhancing excitability.
- Burbot INa density was high with a significantly negative activation curve, indicating adaptation for cold excitability and potentially excitation-contraction coupling.
Conclusions:
- Fish cardiac INa exhibits thermal plasticity that is species-specific, aligning with their ecological niches and lifestyles.
- These INa modifications are crucial for maintaining cardiac function and supporting variable life strategies in cold aquatic environments.
- The study highlights the diverse physiological adaptations of fish hearts to cold, mediated by changes in ion channel function.