Effects of temperature on human L-type cardiac Ca2+ channels expressed in Xenopus oocytes

T. Jeffrey A Allen, G. Mikala

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Temperature normally affects peak L-type Ca2+ channel (CaCh) current with a temperature coefficient (Q10) of between 1.8 and 3.5; in cardiomyocytes attenuating protein kinase A activity increases Q10 whilst activating it lowers Q10. We examine temperature effects using cloned human cardiac CaChs expressed in Xenopus oocytes. Peak inward currents (I(Ba)) through expressed CaChs (i.e. α(1C) α2/δ(a) β(1b)) exhibited a Q10 of 5.8±0.4 when examined between 15 and 25°C. The nifedipine-sensitive I(Ba) exhibited a higher Q10 of 8.7±0.5, whilst the nifedipine-insensitive I(Ba) exhibited Q10 of 3.7±0.3. Current/voltage (I/V) relationships shifted to negative potentials on warming. Using instead a different CaCh β subunit isoform, β(2c), gave rise to an I(Ba) similar to those expressed using β(1b). We utilized a carboxyl deletion mutant, α(1C-Δ1633), to determine the temperature sensitivity of the pore moiety in the absence of auxiliary subunits; I(Ba) through this channel exhibited a Q10 of 9.3±0.3. However, the Q10 for macroscopic conductance was reduced compared to that of heteromeric channels; decreasing from 5.0 (i.e. α(1C) α2/δ(a) β(1b)) and 3.9 (i.e. α(1C) α2/δ(a) β(2c)) to 2.4 (α(1C-Δ1633)). These observations differ markedly from those made in studies of cardiomyocytes, and suggest that enhanced sensitivity may depend on the membrane environment, channel assembly or other regulatory factors.

Original languageEnglish
Pages (from-to)238-247
Number of pages10
JournalPflugers Archiv European Journal of Physiology
Volume436
Issue number2
DOIs
Publication statusPublished - 1998

Fingerprint

Xenopus
Oocytes
Nifedipine
Temperature
Cardiac Myocytes
Cyclic AMP-Dependent Protein Kinases
Ion Channels
Thermal effects
Protein Isoforms
Electric potential

Keywords

  • Calcium
  • Heart
  • Hypothermia
  • Phosphorylation
  • Protein kinase A

ASJC Scopus subject areas

  • Physiology

Cite this

Effects of temperature on human L-type cardiac Ca2+ channels expressed in Xenopus oocytes. / Allen, T. Jeffrey A; Mikala, G.

In: Pflugers Archiv European Journal of Physiology, Vol. 436, No. 2, 1998, p. 238-247.

Research output: Contribution to journalArticle

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