Increases of T-type Ca2+ current in heart cells of the cardiomyopathic hamster

In the present study, the whole-cell voltage clamp technique was used in order to record the T-and L-type Ca2+ currents in single heart cells of newborn and young normal and hereditary cardiomyopathic hamsters. Our results showed that the I/V relationship curve as well as the kinetics of the L-type Ca2+ currents (I-Ca(L)) in both normal and cardiomyopathic heart cells were the same. However, the proportion of myocytes from normal heart hamster that showed L-type I-Ca was less than that of heart cells from cardiomyopathic hamster. The I/V relationship curve of the T-type I-Ca (I-Ca(T)) was the same in myocytes of both normal and cardiomyopathic hamsters. The main differences between I-Ca(T) of cardiomyopathic and normal hamster are a larger window current and the proportion of ventricular myocytes that showed this type of current in cardiomyopathic hamster. The high density of I-Ca(T) as well as the large window current and proportion of myocytes showing I-Ca(T) may explain in part Ca2+ overload observed in cardiomyopathic heart cells of the hamster.