[Evidence for expression of a nifedipine resistant L-type calcium current in human atrial cardiomyocytes].
In the heart, two types of calcium currents were described, the L- and T-type. In addition to these two types, a dihydropyridine-resistant Ca2+ component has been described to be up-regulated in rat ventricular cardiomyocytes during their differentiation- dedifferentiation process. The aim of our study is to examine if such calcium current component is present in human cardiomyocytes. The patch clamp technique was used to record Ca2+ current in atrial cells. In the presence of 2 microM nifedipine, residual current was activated (-2.7 +/- 0.7 pA/pF, n = 6) in the same voltage range as the L-type, nifedipine-sensitive Ca2+ current (-2.1 +/- 0.4 pA/pF, n = 6), but its steady-state inactivation was negatively shifted by 10 mV. This nifedipine-resistant Ca2+ current was completely blocked by 500 microM cadmium chloride and significantly enhanced by 1 microM isoproterenol (-7.5 +/- 0.5 pA/pF, n = 6; p <0.01). These results give evidence that a nifedipine-resistant Ca2+ current, similar to the one which has been shown to be developmentally expressed in rat ventricular cardiomyocytes, is observed in human atrial cells. Its molecular identity, its expression level as well as its role in pathophysiologic conditions remain to be studied.
Farès
Nassim
N
Laboratoire de Physiologie, Faculté de Médecine, Université Saint-Joseph (FM - USJ), Beyrouth, Liban. nassim.fares@usj.edu.lb
Jebara
Victor
V
Corbi
Pierre
P
Bois
Patrick
P
Potreau
Daniel
D
D019256:Cadmium Chloride; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects*; D004095:Dihydropyridines / Q000627:therapeutic use; D006325:Heart Atria / Q000294:innervation*; D006801:Humans; D066298:In Vitro Techniques; D032383:Myocytes, Cardiac / Q000187:drug effects*; D009543:Nifedipine / Q000627:therapeutic use; D018408:Patch-Clamp Techniques
D015220:Calcium Channels; D004095:Dihydropyridines; D009543:Nifedipine; D019256:Cadmium Chloride; D002118:Calcium