6533b86efe1ef96bd12cbc61

RESEARCH PRODUCT

Effects of Quinine and Quinidine on the Transient Outward and on the L-Type Ca<sup>2+</sup> Current in Rat Ventricular Cardiomyocytes

subject

description

The effects of the enantiomers quinine and quinidine on the transient outward current (I<sub>to</sub>) and on the L-type Ca<sup>2+</sup> current (I<sub>Ca</sub>) 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<sub>to</sub> and I<sub>Ca</sub>; the half-maximal effects on I<sub>to</sub> were achieved at 11 and 15 µmol/l, respectively, and those on I<sub>Ca</sub> at 14 and 10 µmol/l, respectively. At 0.2 Hz, both drugs depressed the magnitude of I<sub>to</sub>, but not that of I<sub>Ca</sub>. 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<sub>to</sub> or I<sub>Ca</sub>. It is concluded that neither the different chemical structure nor the amount of protonation of quinine and quinidine controls their effects on I<sub>to</sub> or I<sub>Ca</sub>.