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First published online July 2, 2004
Journal of Experimental Biology 207, 2823-2833 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01103

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Temperature acclimation modifies Na⁺ current in fish cardiac myocytes

Jaakko Haverinen and Matti Vornanen^*

University of Joensuu, Department of Biology, PO Box 111, 80101 Joensuu, Finland

View larger version (31K): [in a new window]   Fig. 1. Voltage-dependence of INa in ventricular myocytes of crucian carp, rainbow trout and burbot hearts. Currents were elicited from a holding potential of –120 mV with 60 ms depolarising pulse between –100 and +70 mV (top). (A) Representative recordings of INa from cold-acclimated (c.a.) fish at +4°C. (B) Results shown as means ± S.E.M. (N=9–16). I–V curves from warm-acclimated (w.a.; closed symbols) and c.a. (open symbols) fish are superimposed to allow direct comparisons between acclimation groups at physiological body temperatures (+4°C/+18°C) and at the common experimental temperature (11°C). See Materials and methods for details.

View larger version (32K): [in a new window]   Fig. 2. Steady-state activation (mx) and inactivation (hx) of INa in ventricular myocytes of crucian carp, rainbow trout and burbot heart. (A) Voltage protocol for steady-state inactivation and representative recordings of INa from c.a. fish at +4°C. Steady-state activation curves were constructed from the I–V curves of Fig. 1 as explained in Materials and methods. (B) Voltage-dependence of steady-state activation and inactivation for w.a. (closed symbols) and c.a. (open symbols) fish (means ± S.E.M.; N=7–21).

View larger version (25K): [in a new window]   Fig. 3. Development of rested-state inactivation of INa in ventricular myocytes of crucian carp, rainbow trout and burbot hearts. (A) Voltage protocol and representative recordings of INa; (B) results shown as means ± S.E.M. (N=6–13). Increased duration of the prepulse at –60 mV reduces INa elicited by the test pulse to –20 mV for 30 ms.

View larger version (24K): [in a new window]   Fig. 4. Recovery of INa from inactivation (reactivation) in ventricular myocytes of crucian carp, rainbow trout and burbot heart. (A) Voltage protocol and representative recordings of INa; (B) values shown as means ± S.E.M. (N=6–19). The amplitude of INa elicited by test pulses to –20 mV for 100 ms increases as function of the time interval between the prepulse P1 and the test pulse P2; see Materials and methods for details.

View larger version (20K): [in a new window]   Fig. 5. Voltage-dependence of inactivation kinetics of INa in ventricular myocytes of crucian carp, rainbow trout and burbot heart. (A) Representative recordings of INa at –20 mV; (B) results from 5–16 myocytes (means ± S.E.M.).

View larger version (13K): [in a new window]   Fig. 6. Charge transfer by INa in ventricular myocytes of crucian carp, rainbow trout and burbot heart. The transferred charged was obtained by integrating the inward current at –20 mV. The values were normalized for cell size by dividing them by membrane capacitance. An asterisk denotes a statistically significant (P<0.01) difference from the values of the burbot heart.