Dual effects of endothelin-1 on the L-type Ca2+ current in ventricular cardiomyocytes

The effects of endothelin-1 on the L-type Ca2+ current were studied in rabbit ventricular cardiomyocytes, using both the 'perforated' and the conventional 'ruptured' whole-cell patch-clamp techniques. Endothelin-1 exerts a dual effect on ventricular cardiomyocytes using experimental conditions which minimize intracellular dialysis; endothelin-1 produced both an increase (10(-9) M) and a decrease (10(-8) M) in the L-type Ca2+ current using the perforated patch-clamp technique. However, using the ruptured patch-clamp technique, endothelin-1 produced a similar decrease in L-type Ca2+ current at 10(-8) M, but no effect was observed at a concentration of 10(-9) M. These effects suggest multiplicity in the receptor-effector coupling mechanism.