Properties and modulation of Ca channels in adult human atrial cells

Ouadid, H.; Seguin, J; Richard, Sylvain; Chaptal, P.A.; Nargeot, Joël

doi:10.1016/0022-2828(91)90037-m

Cited by 59 publications

(23 citation statements)

References 26 publications

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“…These findings indicated significant species differences in I CaT expression. A previous study reported that I CaT was absent in adult human atrial (12) and ventricular cells. In large animals (i.e., pigs and humans), Ca 2+ may be exclusively carried via I CaL , and not I CaT .…”

Section: Species Differences Of Tcc Densitymentioning

confidence: 88%

“…Much information has been obtained for possible roles of I CaL in normal and diseased tissues. However, I CaT has never been recorded in human cardiomyocytes (12,42). In addition, patch clamp experiments using various mammalian species demonstrated that current density of I CaT was large in small animals and became smaller as body size increased (mouse > guinea pig > rabbit > pig).…”

Section: +mentioning

confidence: 99%

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Pathophysiological Significance of T-type Ca2+ Channels: Properties and Functional Roles of T-type Ca2+ Channels in Cardiac Pacemaking

Ono

Iwamoto

2005

J Pharmacol Sci

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Abstract. Calcium channels are essential for excitation-contraction coupling and pacemaker activity in cardiac myocytes. While L-type Ca 2+ channels (LCC) have been extensively studied, functional roles of T-type channels (TCC) in native cardiac myocytes are still debatable. TCC are activated at more negative membrane potentials than LCC and therefore facilitate slow diastolic depolarization in sinoatrial node cells. Recent studies showed that selective inhibition of TCC produced a marked slowing of the pacemaker rhythm, indicating that contribution of TCC to cardiac automaticity was relatively larger than what had been speculated in previous studies. To re-evaluate TCC, we measured current density and kinetics of TCC in sinoatrial node cells of various mammalian species. Current density of TCC was larger in mice and guinea pigs than in rabbit and porcine sinoatrial node cells. Interestingly, few or no obvious TCC were recorded in porcine sinoatrial node cells. Furthermore, it was demonstrated that TCC could be enhanced by several vasoactive substances, thereby increasing spontaneous firing rate of sinoatrial node cells. TCC may, at least in part, account for different heart rates among various mammalian species. In addition, TCC might be involved in physiological and / or pathophysiological modulations of the heart rate.

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Section: Species Differences Of Tcc Densitymentioning

confidence: 88%

Section: +mentioning

confidence: 99%

Pathophysiological Significance of T-type Ca2+ Channels: Properties and Functional Roles of T-type Ca2+ Channels in Cardiac Pacemaking

Ono

Iwamoto

2005

J Pharmacol Sci

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“…For example T-type currents are prominent throughout the guinea pig and hamster heart but virtually absent in adult ventricular myocytes of rat, cat, and dog. Although Ca v 3.2 was cloned from a human heart cDNA library, T-type currents have not been detected in human myocytes (39,235,313).…”

Section: Heartmentioning

confidence: 99%

Molecular Physiology of Low-Voltage-Activated T-type Calcium Channels

Perez‐Reyes

2003

Physiological Reviews

1,518

1,446

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T-type Ca2+ channels were originally called low-voltage-activated (LVA) channels because they can be activated by small depolarizations of the plasma membrane. In many neurons Ca2+ influx through LVA channels triggers low-threshold spikes, which in turn triggers a burst of action potentials mediated by Na+ channels. Burst firing is thought to play an important role in the synchronized activity of the thalamus observed in absence epilepsy, but may also underlie a wider range of thalamocortical dysrhythmias. In addition to a pacemaker role, Ca2+ entry via T-type channels can directly regulate intracellular Ca2+ concentrations, which is an important second messenger for a variety of cellular processes. Molecular cloning revealed the existence of three T-type channel genes. The deduced amino acid sequence shows a similar four-repeat structure to that found in high-voltage-activated (HVA) Ca2+ channels, and Na+ channels, indicating that they are evolutionarily related. Hence, the α1-subunits of T-type channels are now designated Cav3. Although mRNAs for all three Cav3 subtypes are expressed in brain, they vary in terms of their peripheral expression, with Cav3.2 showing the widest expression. The electrophysiological activities of recombinant Cav3 channels are very similar to native T-type currents and can be differentiated from HVA channels by their activation at lower voltages, faster inactivation, slower deactivation, and smaller conductance of Ba2+. The Cav3 subtypes can be differentiated by their kinetics and sensitivity to block by Ni2+. The goal of this review is to provide a comprehensive description of T-type currents, their distribution, regulation, pharmacology, and cloning.

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“…There is a report that the T-type Ca 2+ current is absent in human atria (15). However, this does not necessarily indicate that the T-type Ca 2+ current is absent in the human sinoatrial node.…”

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confidence: 90%

Species Difference in the Contribution of T-Type Calcium Current to Cardiac Pacemaking as Revealed by R(−)-Efonidipine

et al. 2008

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Abstract. The contribution of the T-type Ca 2+ current to cardiac pacemaking was examined in isolated right atrial tissue from the mouse, guinea pig, and rabbit using a specific blocker, R(−)-efonidipine. At 10 −6 M, R(−)-efonidipine produced negative chronotropy, which was prominent in the mouse and small but significant in the guinea pig. No effect was observed in the rabbit. Microelectrode recordings revealed that R(−)-efonidipine significantly prolongs the pacemaker (phase 4) depolarization of the sinoatrial-node action potential in the mouse and guinea pig. These results provide the first pharmacological evidence that the contribution of T-type Ca 2+ current to cardiac pacemaking differs among experimental animal species.

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Properties and modulation of Ca channels in adult human atrial cells

Cited by 59 publications

References 26 publications

Pathophysiological Significance of T-type Ca2+ Channels: Properties and Functional Roles of T-type Ca2+ Channels in Cardiac Pacemaking

Pathophysiological Significance of T-type Ca2+ Channels: Properties and Functional Roles of T-type Ca2+ Channels in Cardiac Pacemaking

Molecular Physiology of Low-Voltage-Activated T-type Calcium Channels

Species Difference in the Contribution of T-Type Calcium Current to Cardiac Pacemaking as Revealed by R(−)-Efonidipine

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