Résumé
The molecular mechanisms underlying the developmental regulation of L-type voltage-dependent Ca2+ channels (VDCCs) are still unknown. In this study, we have characterized the expression patterns of skeletal (α1S) and cardiac (α1C) L-type VDCCs during cardiogenic differentiation in H9C2 cells that derived from embryonic rat heart. We report that chronic treatment of H9C2 cells with 10 nm all-trans-retinoic acid (all-trans-RA) enhanced cardiac Ca2+ channel expression, as demonstrated by reverse transcription-polymerase chain reaction, immunoblotting, and indirect immunofluorescence studies, as well as patch-clamp experiments. In addition, RA treatment prevented expression of functional skeletal L-type VDCCs, which were restricted to myotubes that spontaneously appear in control H9C2 cultures undergoing myogenic transdifferentiation. The use of specific skeletal and cardiac markers indicated that RA, by preventing myogenic transdifferentiation, preserves cardiac differentiation of this cell line. Altogether, we provide evidence that cardiac and skeletal subtype-specific L-type Ca2+ channels are relevant functional markers of differentiated cardiac and skeletal myocytes, respectively. In conclusion, our data demonstrate that in vitro RA stimulates cardiac (α1C) L-type Ca2+ channel expression, therefore supporting the hypothesis that the RA pathway might be involved in the tissue specific expression of Ca2+ channels in mature cardiac cells.