Conductive properties of muscle fibres from green sunfish (Lepomis cyanellus) acclimated to different temperatures were examined. The relative membrane permeability to chloride and potassium ions, PCl/PK, measured at acclimation temperature, was approximately 7.0 after acclimation at 25 degrees C and 1.3 after acclimation at 7 degrees C. This difference was due to a six-fold reduction in the membrane chloride conductance upon acclimation to 7 degrees C as compared to 25 degrees C-acclimated fibres. Mean (+/- S.E.M.) values of the chloride conductance were 554 +/- 68 microseconds cm-2 in warm-acclimated sunfish, and 75 +/- 9 microseconds cm-2 in cold-acclimated sunfish. Membrane capacitance also differed significantly between the two acclimation groups. When the temperature was varied acutely, the magnitude of the chloride conductance exhibited a maximum Q10 of only 1.9, compared with a Q10 of 3.0 associated with acclimation. Upon transferring 25 degrees C-acclimated sunfish to holding tanks at 7 degrees C, the total membrane resistance exhibited a sigmoidal increase over about 14 days, and a steady membrane capacitance was achieved in about 10 days. For 7 degrees C-acclimated sunfish, transferred to 25 degrees C, resistance showed a sigmoidal decrease over 10 days and capacitance was steady after 8 days. The results indicate that thermal acclimation of the muscle membrane involves cellular regulatory processes which underlie significant changes in the electrical properties of the fibre.
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Klein et al. (1985) studied this question.
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