Temperature-dependence of L-type Ca super(2+) current in ventricular cardiomyocytes of the Alaska blackfish (Dallia pectoralis)

• Published in: Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Biochemical, systemic, and environmental physiology, 2015-12, Vol.185 (8), p.845-858
• Main Authors: Kubly, Kerry L, Stecyk, Jonathan AW
• Format: Article
• Language: English
• Subjects: Dallia pectoralis
• ISSN: 0174-1578; 1432-136X
• DOI: 10.1007/s00360-015-0931-7

To lend insight into the overwintering strategy of the Alaska blackfish (Dallia pectoralis), we acclimated fish to 15 or 5 degree C and then utilized whole-cell patch clamp to characterize the effects of thermal acclimation and acute temperature change on the density and kinetics of ventricular L-type Ca super(2+) current (I sub(Ca)). Peak I sub(Ca) density at 5 degree C (-1.1 plus or minus 0.1 pA pF super(-1)) was 1/8th that at 15 degree C (-8.8 plus or minus 0.6 pA pF super(-1)). However, alterations of the Ca super(2+)- and voltage-dependent inactivation properties of L-type Ca super(2+) channels partially compensated against the decrease. The time constant tau ( tau ) for the kinetics of inactivation of I sub(Ca) was ~4.5 times greater at 5 degree C than at 15 degree C, and the voltage for half-maximal inactivation was shifted from -23.3 plus or minus 1.0 mV at 15 degree C to -19.8 plus or minus 1.2 mV at 5 degree C. These modifications increase the open probability of the channel and culminate in an approximate doubling of the L-type Ca super(2+) window current, which contributes to approximately 15 % of the maximal Ca super(2+) conductance at 5 degree C. Consequently, the charge density of I sub(Ca) (Q sub(Ca)) and the total Ca super(2+) transferred through the L-type Ca super(2+) channels ( Delta [Ca super(2+)]) were not as severely reduced at 5 degree C as compared to peak I sub(Ca) density. In combination, the results suggest that while the Alaska blackfish substantially down-regulates I sub(Ca) with acclimation to low temperature, there is sufficient compensation in the kinetics of the L-type Ca super(2+) channel to support the level of cardiac performance required for the fish to remain active throughout the winter.