T-type calcium current is expressed in dedifferentiated adult rat ventricular cells in primary culture.

Ventricular myocytes isolated from the heart of adult rats were able do dedifferentiate within 7 days in primary culture using a medium containing 10% fetal calf serum. Calcium current was recorded in these cells by means of the whole cell patch clamp technique and compared to the calcium current obtained in freshly isolated myocytes and in non dedifferentiated cultured myocytes. In dedifferentiated cardiomyocytes, both T-type (ICa-T) and L-type (ICa-L) calcium current components were recorded while only L-type was observed in freshly isolated and in non dedifferentiated cultured myocytes. ICa-T was separated from ICa-L through its voltage dependence and its pharmacology. These results demonstrate that ICa-T which has been shown to be present at the neonatal stage but absent in adult ventricular cells can be reexpressed when adult cells were dedifferentiated in culture. Its possible involvement in development of cardiac cells and in electrophysiological properties leading to spontaneous activity is discussed.