Barnidipine block of L-type Ca2+ channel currents in rat ventricular cardiomyocytes

The effects of barnidipine and nifedipine on L-type Ca2+ current (ICa(L)) were investigated in ventricular cardiomyocytes from rats. Both barnidipine and nifedipine reduced ICa(L) in a concentration and voltage dependent manner; the EC50 were 80 and 130 nM at a holding potential of −80 mV, respectively, and 18 and 6 nM at −40 mV, respectively. Both drugs induced a leftward shift of the steady-state inactivation curve of ICa(L). Using a twin pulse protocol, the relationships between the amount of block of ICa(L) by either drug, seen during the second pulse, and the length of the first pulse were described by monoexponential functions reflecting onset of block, dependent on drug concentration…