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A major action of the antiarrhythmic agent quinidine is prolongation of cardiac repolarization. In these experiments, the time-dependent effects of quinidine on the delayed rectifier potassium current, I,, a current contributing to cardiac repolarization, were investigated in acutely disaggregated guinea pig ventricular myocytes using the whole-cell recording configuration of the patch-clamp me...

From the University of Michigan Medical Center, Ann Arbor, Mich. This work was supported by Grants from the Michigan Heart Association and U.S. Public Health Service, National Institutes of Health HE 07406-05. Manuscript received October 3, 1969, accepted February 6, 1970. Address for reprints: Ernest W. Reynolds, Jr., MD, University of Michigan Medical Center, Ann Arbor, Mich. 48104. Combining...

Background and Objectives: Drug-induced electrocardiographic QT interval prolongation is associated with the occurrence of a potentially lethal form of polymorphic ventricular tachycardia, termed ‘torsades de pointes’ (TdP). Women are at greater risk for the development of drug-induced TdP. To determine whether this may be the result of gender-specific differences in the effect of quinidine on ...

Accumulating evidence has proved that potassium channels (K+ channels) are involved in regulating cell proliferation, cell cycle progression and apoptosis of tumor cells. However, the precise cellular mechanisms are still unknown. In the present study, we investigated the effect and mechanisms of quinidine, a commonly used voltage-gated K+ channel blocker, on cell proliferation and apoptosis of...

Quinidine and its stereoisomer quinine suppress various membrane conductances in a variety of cells Recently quinidine has been classified as a putative blocker of the Na-Ca exchange in heart muscle (Mentrard et al. 1984; Chapman et al. 1984). The effects of quinidine on the contractile responses of the ureter muscle of the guinea-pig associated with both the entry of Ca via voltage-operated Ca...

It has been demonstrated that the activity of cytochrome P450 (CYP)3A4 in certain cases is stimulated by quinidine (positive heterotropic cooperativity). We report herein that the 4'- and 10-hydroxylation of S- and R-warfarin are enhanced in human liver microsomal incubations containing quinidine. These reactions were catalyzed by CYP3A4, based on data derived from immunoinhibitory studies, wit...

BACKGROUND Cardiac cells display rate-dependent beat-to-beat variations in action-potential duration (APD), action potential amplitude (APA), and excitability during periodic stimulation. We hypothesized that quinidine causes a marked increase in the variability of APD, APA, and excitability of ventricular cells isolated from quinidine-toxic, arrhythmic ventricles. METHODS AND RESULTS Action ...

Since quinidine is one of the few agents available to treat and prevent ventricular arrhythmias in ambulatory patients, its hemodynamic effects have been reevaluated. When given in therapeutic doses to anesthetized mongrel dogs, quinidine significantly reduced heart rate, aortic pressure and flow, but it did not significantly change the first derivative of the left ventricular pressure curve (l...