Characterization of a Ca2+-activated nonselective cation channel during dedifferentiation of cultured rat ventricular cardiomyocytes.
Cardiac hypertrophy is associated with electrical activity modifications, including sustained depolarization, that lead to a propensity for arrhythmias. The ionic currents underlying the sustained depolarization are not well defined. Similar modifications were reported on adult rat cardiomyocytes in primary culture undergoing dedifferentiation. Using the single-channel measurements on these cells, we identified the appearance of a Ca2+-activated nonselective cation channel (NSCCa) during the dedifferentiation process. In excised inside-out patches the channel presented a linear I/V relationship with a conductance of 26.5 pS. It was equally selective for Na+ and K+ and impermeable to Cl- and Ca2+ ions. The open probability increased with depolarization and with rise in intracellular calcium concentration. The channel activity was reduced by intracellular ATP and suppressed by flufenamic acid. Channel detection increased after incubation with a purinergic receptor agonist (ATPgS) or a PKC activator (PMA). Furthermore, occurrence of the channel developed during the culture. Absent at one day in vitro (d.i.v.), channel activity was present in 5, 46, 27 and 19% of patches after 4, 7, 14 and 21 d.i.v., respectively. We suggest that the channel may be associated with pro-arrhythmic signaling, in particular during the release of transmitters from autonomic nerve endings in the hypertrophied hearts.
Guinamard
R
R
Laboratoire des Biomembranes et Signalisation Cellulaire, CNRS UMR 6558, Université de Poitiers, 86022 Poitiers Cedex, France. romain.guinamard@univ-poitiers.fr
Rahmati
M
M
Lenfant
J
J
Bois
P
P
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D004553:Electric Conductivity; D005439:Flufenamic Acid / Q000494:pharmacology; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D011493:Protein Kinase C / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000494:pharmacology; D016276:Ventricular Function
D007473:Ion Channels; C022571:adenosine 5'-O-(3-thiotriphosphate); D005439:Flufenamic Acid; D000255:Adenosine Triphosphate; D012964:Sodium; D011493:Protein Kinase C; D011188:Potassium; D002118:Calcium