Effects of the enantiomers of the dihydropyridine derivative 202-791 on contractility, coronary flow and ischemia-related arrhythmias in rat heart.

The (+)-enantiomer of the dihydropyridine 202-791 produced coronary constrictor and positive inotropic effects in Langendorff-perfused rat hearts whereas (--)-202-791 showed coronary dilator and negative inotropic effects. Both enantiomers showed the vascular effects at lower concentrations than the myocardial effects. Furthermore, the (+)-enantiomer significantly increased whilst the (--)-enantiomer reduced the number of ventricular ectopic beats occurring during coronary ligation. Arrhythmia-enhancing effects must therefore be considered when the potential therapeutic uses of calcium channel activators are discussed.