PUB - Publikationen an der Universität Bielefeld

The effects of the enantiomers quinine and quinidine on the transient outward current (I_to) and on the L-type Ca²⁺ current (I_Ca) were investigated in rat ventricular cardiomyocytes using the patch-clamp technique. At a stimulation frequency of 2 Hz, both quinine and quinidine depressed the magnitude of I_to and I_Ca; the half-maximal effects on I_to were achieved at 11 and 15 µmol/l, respectively, and those on I_Ca at 14 and 10 µmol/l, respectively. At 0.2 Hz, both drugs depressed the magnitude of I_to, but not that of I_Ca. A change in extracellular pH from 7.3 to 8.3 did not significantly influence the effects of the drugs (which are protonated to 98% at pH 7.3) on I_to or I_Ca. It is concluded that neither the different chemical structure nor the amount of protonation of quinine and quinidine controls their effects on I_to or I_Ca.