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Reexpression of the Nifedipine‐Resistant Calcium Channel During Dedifferentiation of Adult Rat Ventricular Cardiomyocytes
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International audience. Nifedipine‐Resistant Calcium Current. Introduction: Using an adult rat ventricular culture model and whole‐cell patch‐clamp technique, we investigated whether the nifedipine‐resistant calcium current observed at the neonatal stage but not at the adult stage could be reobserved under dedifferentiating conditions. Methods and Results: Application of 2 μ M nifedipine totally inhibited the inward calcium current (carried by 5 mM Ba 2+ ) in freshly isolated cells from adult rat heart, but it failed to block it completely when cells are cultured for 8 to 12 days. Dose‐response curves of nifedipine in the range from 2 to 50 μ M showed a residual current that represented, in the presence of 2 μ M nifedipine, 16.4% ± 1.8% ( n = 10 ) and 20.4% ± 1.5% ( n = 10 ) of the total current in 8‐ and 12‐day‐old cultured cells, respectively. In these conditions, its density at 0 mV increased slightly during culture ( −2.1 ± 0.2 pA/pF, n = 7, and −3.2 ± 0.4 pA/pF, n = 8, after 8 and 12 days in culture, respectively ), without modification in the current‐tovoltage curve, as well as in kinetics properties. Conclusion: These results show that nifedipine‐resistant calcium current, which has been shown to be developmentally regulated in rat ventricular cardiomyocytes, can be reexpressed in cultured‐dedifferentiated cells. Its possible expression and implication in physiopathologic function are suggested.
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