Effects of mechanical uncouplers, diacetyl monoxime, and cytochalasin-D on the electrophysiology of perfused mouse hearts.
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-naphthyl]vinyl]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
Linda C
LC
Dept. of Cell Biology and Physiology, S314 Biomedical Science Tower, University of Pittsburgh School of Medicine, 3500 Terrace Street, Pittsburgh, PA 15261, USA.
Wolk
Robert
R
Choi
Bum-Rak
BR
Watkins
Simon
S
Plan
Patricia
P
Shah
Anisha
A
Salama
Guy
G
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000188:drug therapy / Q000503:physiopathology; D002118:Calcium / Q000378:metabolism; D015638:Cytochalasin D / Q000494:pharmacology*; D003931:Diacetyl / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004594:Electrophysiology; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D006321:Heart / Q000187:drug effects; D006575:Heterocyclic Compounds, 3-Ring; D066298:In Vitro Techniques; D007700:Kinetics; D051379:Mice; D008815:Mice, Inbred Strains; D009200:Myocardial Contraction / Q000187:drug effects*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology*; D019188:Organ Preservation Solutions / Q000494:pharmacology*; D010477:Perfusion
D005456:Fluorescent Dyes; D006575:Heterocyclic Compounds, 3-Ring; D019384:Nucleic Acid Synthesis Inhibitors; D019188:Organ Preservation Solutions; C068483:rhod-2; C004717:diacetylmonoxime; D015638:Cytochalasin D; D003931:Diacetyl; D002118:Calcium