title: Temperature-dependence of L-type Ca(2+) current in ventricular cardiomyocytes of the Alaska blackfish (Dallia pectoralis).
abstract: To lend insight into the overwintering strategy of the Alaska blackfish (Dallia pectoralis), we acclimated fish to 15 or 5 °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(2+) current (I Ca). Peak I Ca density at 5 °C (-1.1 ± 0.1 pA pF(-1)) was 1/8th that at 15 °C (-8.8 ± 0.6 pA pF(-1)). However, alterations of the Ca(2+)- and voltage-dependent inactivation properties of L-type Ca(2+) channels partially compensated against the decrease. The time constant tau (τ) for the kinetics of inactivation of I Ca was ~4.5 times greater at 5 °C than at 15 °C, and the voltage for half-maximal inactivation was shifted from -23.3 ± 1.0 mV at 15 °C to -19.8 ± 1.2 mV at 5 °C. These modifications increase the open probability of the channel and culminate in an approximate doubling of the L-type Ca(2+) window current, which contributes to approximately 15% of the maximal Ca(2+) conductance at 5 °C. Consequently, the charge density of I Ca (Q Ca) and the total Ca(2+) transferred through the L-type Ca(2+) channels (Δ[Ca(2+)]) were not as severely reduced at 5 °C as compared to peak I Ca density. In combination, the results suggest that while the Alaska blackfish substantially down-regulates I Ca with acclimation to low temperature, there is sufficient compensation in the kinetics of the L-type Ca(2+) channel to support the level of cardiac performance required for the fish to remain active throughout the winter.
authors.affiliation: Department of Biological Sciences, University of Alaska Anchorage, 3211 Providence Drive, Conoco Philips Integrated Science Building, Anchorage, AK, 99508, USA. klkubly@alaska.edu.
authors.forename: Kerry L
authors.initials: KL
authors.lastname: Kubly
authors.affiliation: Department of Biological Sciences, University of Alaska Anchorage, 3211 Providence Drive, Conoco Philips Integrated Science Building, Anchorage, AK, 99508, USA.
authors.forename: Jonathan A W
authors.initials: JA
authors.lastname: Stecyk
mesh_terms: D000064:Acclimatization; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D020013:Calcium Signaling; D003080:Cold Temperature; D005399:Fishes / Q000378:metabolism*; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism*; D015640:Ion Channel Gating; D007700:Kinetics; D008564:Membrane Potentials; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D012621:Seasons
chemical_list: D020746:Calcium Channels, L-Type; D002118:Calcium
keywords: Electrophysiology; Heart; I Ca; Thermal acclimation