T-type calcium current in electrical activity of cardiomyocytes isolated from rabbit pulmonary vein.
BACKGROUND
Pulmonary veins (PVs) are known to initiate paroxysmal atrial fibrillation. T-type calcium current (I(Ca-T)) has a role in normal and abnormal automaticity of cardiomyocytes. The aim of this study was to evaluate whether I(Ca-T) contributes to PV electrical activity.


RESULTS
By whole-cell clamp techniques in rabbit myocytes, I(Ca-T) was identified in 12 (39%) of 31 PV cardiomyocytes with pacemaker activity, 2 (9%) of 23 PV cardiomyocytes without pacemaker activity, and 2 (15%) of 13 atrial myocytes (P < 0.05). Maximum I(Ca-L) and I(Ca-T) densities from PV cardiomyocytes with pacemaker activity were 6.87 +/- 2.17 pA/pF and 1.38 +/- 0.69 pA/pF, respectively. Nickel (40 microM) decreased the spontaneous activity in 5 (36%) of 14 PV cardiomyocytes (3.1 +/- 0.6 Hz vs 2.2 +/- 0.5 Hz, P < 0.05), reduced the amplitudes of delayed after depolarization from 13 +/- 1 mV to 7 +/- 1 mV (n = 4, P < 0.05) and inhibited transient inward currents from 1.2 +/- 0.2 pA/pF to 0.7 +/- 0.1 pA/pF (n = 11, P < 0.01).


CONCLUSIONS
We conclude that I(Ca-T) contributes to PV pacemaker activity and triggered activity, which are of functional importance in PV arrhythmogenesis.
Chen
Yao-Chang
YC
Department of Biomedical Engineering, National Defense Medical Center, Taiwan, Republic of China.
Chen
Shih-Ann
SA
Chen
Yi-Jen
YJ
Tai
Ching-Tai
CT
Chan
Paul
P
Lin
Cheng-I
CI
D000200:Action Potentials; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology*; D020747:Calcium Channels, T-Type / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology*; D009532:Nickel / Q000494:pharmacology; D011667:Pulmonary Veins / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits
D020747:Calcium Channels, T-Type; D009532:Nickel