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 (ICa(L)) in both normal and cardiomyopathic heart cells were the same. However, the proportion of myocytes from normal heart hamster that showed L-type ICa was less than that of heart cells from cardiomyopathic hamster. The I/V relationship curve of the T-type ICa (ICa(T)) was the same in myocytes of both normal and cardiomyopathic hamsters. The main differences between ICa(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 ICa(T) as well as the large window current and proportion of myocytes showing ICa(T) may explain in part Ca2+ overload observed in cardiomyopathic heart cells of the hamster.