Temperature acclimation modifies Na+ current in fish cardiac myocytes
The present study was designed to test the hypothesis that temperature acclimation modifies sarcolemmal Na+ current (I Na ) of the fish cardiac myocytes differently depending on the animal's lifestyle in the cold. Two eurythermal fish species with different physiological strategies for survivin...
| Published in: | Journal of Experimental Biology |
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| Main Authors: | , |
| Format: | Text |
| Language: | English |
| Published: |
Company of Biologists
2004
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| Subjects: | |
| Online Access: | http://jeb.biologists.org/cgi/content/short/207/16/2823 https://doi.org/10.1242/jeb.01103 |
| Summary: | The present study was designed to test the hypothesis that temperature acclimation modifies sarcolemmal Na+ current (I Na ) of the fish cardiac myocytes differently depending on the animal's lifestyle in the cold. Two eurythermal fish species with different physiological strategies for surviving in the cold, a cold-dormant crucian carp ( Carassius carassius L.) and a cold-active rainbow trout ( Oncorhynchus mykiss ), were used in acclimation experiments. The I Na of carp and trout were also compared with I Na of a cold stenothermal burbot ( Lota lota ). In accordance with the hypothesis, cold-acclimation decreased the density of I Na in crucian carp and increased it in rainbow trout, suggesting depression of impulse conduction in cold-acclimated carp and positive compensation of impulse propagation in cold-acclimated trout. The steady-state activation curve of trout I Na was shifted by 6 mV to more negative voltages by cold acclimation, which probably lowers the stimulus threshold for action potentials and further improves cardiac excitability in the cold. In burbot myocytes, the I Na density was high and the position of the steady-state activation curve on the voltage axis was even more negative than in trout or carp myocytes, suggesting that the burbot I Na is adapted to maintain high excitability and conductivity in the cold. The I Na of the burbot heart differed from those of carp and trout in causing four times larger charge influx per excitation, which suggests that I Na may also have a significant role in cardiac excitation–contraction coupling of the burbot heart. In summary, I Na of fish cardiac myocytes shows thermal plasticity that is different in several respects in cold-dormant and cold-active species and thus has a physiologically meaningful role in supporting the variable life styles and habitat conditions of each species. |
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