Effects of mechanical uncouplers, diacetyl monoxime, and cytochalasin-D on the electrophysiology of perfused mouse hearts

• Published in: American journal of physiology. Heart and circulatory physiology 2004-10, Vol.56 (4), p.H1771-H1779
• Main Authors: BAKER, Linda C, WOLK, Robert, CHOI, Bum-Rak, WATKINS, Simon, PLAN, Patricia, SHAH, Anisha, SALAMA, Guy
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Heart; Molecular biology; Rodents; Vertebrates: cardiovascular system
• ISSN: 0363-6135; 1522-1539

Chemical uncouplers diacetyl monoxime (DAM) and cytochalasin D (cyto-D) are used to abolish cardiac contractions in optical studies, yet alter intracellular Ca2+ concentration ([Ca2+]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-naphthyl]vinyl]pyridinium (di-4-ANEPPS) to map [Ca2+]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 (APD75 = 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 [Ca2+]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 [Ca2+]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 [Ca2+]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. [PUBLICATION ABSTRACT]