Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2534020 | European Journal of Pharmacology | 2009 | 7 Pages |
Carvedilol is widely used in the treatment of cardiovascular diseases including atrial fibrillation. T-type Ca2+ channels have been recognized recently in the mechanisms underlying atrial arrhythmias. However, it is unclear whether carvedilol may affect the T-type Ca2+ channel. The present study evaluated the pharmacological effects of carvedilol on T-type calcium current (ICa,T) in the murine HL-1 cell line. ICa,T was recorded by the whole-cell patch–clamp technique. Calcium transient was monitored by the fluorescent dye Fluo-4/AM and confocal laser scanning microscopy. Carvedilol reversibly inhibited ICa,T in a concentration-dependent manner, with an IC50 of 2.1 µM. 3 µM carvedilol was found to decrease the peak ICa,T amplitude at − 20 mV from 20.1 ± 1.8 pA/pF to 10.9 ± 2.1 pA/pF. Carvedilol significantly shifted the steady-state inactivation curve of ICa,T towards more negative potential by 12.8 mV, while the activation curve was not significantly altered. Carvedilol delayed recovery from inactivation of ICa,T, time constant (τ) was 112.4 ± 3.5 ms in control and 270.1 ± 4.7 ms in carvedilol. Carvedilol-induced inhibition rate in ICa,T was enhanced with the increase in stimuli frequency, the inhibitory rate was 23.2 ± 4.1% at 0.2 Hz and 47.2 ± 0.6% at 2 Hz. Carvedilol still produced the significant decrease in the amplitude of ICa,T in the presence of H-89, PKA inhibitor. Carvedilol significantly inhibited the amplitude of the calcium transient in a concentration-dependent manner. These findings indicate that carvedilol inhibits ICa,T in atrial cells by mechanisms involving preferential interaction with the inactivated state of T-type Ca2+ channel.