Diacetyl monoxime and cytochalasin-D increased action potential durations (from 20.0 to 46.6 and 39.9 ms, respectively) and refractory periods, and blocked pacing-induced ventricular tachycardia.
Mechanical uncouplers DAM and cyto-D significantly alter action potential duration, calcium handling, and arrhythmia vulnerability in perfused mouse hearts, which is critical to consider when using them in optical mapping studies.
Chemical uncouplers diacetyl monoxime (DAM) and cytochalasin D (cyto-D) are used to abolish cardiac contractions in optical studies, yet alter intracellular Ca(2+) concentration (Ca(2+)(i)) handling and vulnerability to arrhythmias in a species-dependent manner. The effects of uncouplers were investigated in perfused mouse hearts labeled with rhod-2/AM or 4-beta-[2-(di-n-butylamino)-6-naphthylvinyl]pyridinium (di-4-ANEPPS) to map Ca(2+)(i) transients (emission wavelength = 585 +/- 20 nm) and action potentials (APs) (emission wavelength > 610 nm; excitation wavelength = 530 +/- 20 nm). Confocal images showed that rhod-2 is primarily in the cytosol. DAM (15 mM) and cyto-D (5 microM) increased AP durations (APD(75) = 20.0 +/- 3 to 46.6 +/- 5 ms and 39.9 +/- 8 ms, respectively, n = 4) and refractory periods (45.14 +/- 12.1 to 82.5 +/- 3.5 ms and 78 +/- 4.24 ms, respectively). Cyto-D reduced conduction velocity by 20% within 5 min and DAM by 10% gradually in 1 h (n = 5 each). Uncouplers did not alter the direction and gradient of repolarization, which progressed from apex to base in 15 +/- 3 ms. Peak systolic Ca(2+)(i) increased with cyto-D from 743 +/- 47 (n = 8) to 944 +/- 17 nM (n = 3, P = 0.01) but decreased with DAM to 398 +/- 44 nM (n = 3, P < 0.01). Diastolic Ca(2+)(i) was higher with cyto-D (544 +/- 80 nM, n = 3) and lower with DAM (224 +/- 31, n = 3) compared with controls (257 +/- 30 nM, n = 3). DAM prolonged Ca(2+)(i) transients at 75% recovery (54.3 +/- 5 to 83.6 +/- 1.9 ms), whereas cyto-D had no effect (58.6 +/- 1.2 ms; n = 3). Burst pacing routinely elicited long-lasting ventricular tachycardia but not fibrillation. Uncouplers flattened the slope of AP restitution kinetic curves and blocked ventricular tachycardia induced by burst pacing.
Baker et al. (Tue,) conducted a other in Perfused mouse hearts. Diacetyl monoxime (DAM) and cytochalasin-D (cyto-D) vs. Controls was evaluated on Action potential durations, refractory periods, conduction velocity, and intracellular Ca(2+) concentration transients. Diacetyl monoxime and cytochalasin-D increased action potential durations (from 20.0 to 46.6 and 39.9 ms, respectively) and refractory periods, and blocked pacing-induced ventricular tachycardia.