Differential effects of cytochalasin D and 2,3 butanedione monoxime on isometric twitch force and transmembrane action potential in isolated ventricular muscle: implications for optical measurements of cardiac repolarization.
BACKGROUND
2,3-Butanedione monoxime (BDM) has been widely used to inhibit contraction during optical recordings of cardiac membrane voltage changes, even though it markedly abbreviates cardiac action potentials.


RESULTS
We compared the effects of BDM and of the F-actin disrupter cytochalasin D (cyto D) on isometric twitch force and transmembrane action potentials in isolated canine right ventricular trabeculae superfused with Tyrode's solution (2 mmol/L CaCl2, 37 degrees C) and stimulated at 0.5 Hz. BDM at 10 mmol/L and cyto D at 80 micromol/L were equally effective in reducing peak isometric force to 10%+/-3% (n = 6; mean+/-SEM) and 8%+/-1% (n = 8), respectively. Neither agent significantly altered resting tension. While 10 mmol/L BDM markedly shortened the action potential duration at 90% repolarization (APD90) from 198+/-7 msec to 146+/-9 msec (P < 0.001), 80 micromol/L cyto D had no significant effects on APD90 or on any other action potential parameter. The effects of BDM on peak isometric force and APD were completely reversible after 15 minutes of washout, whereas in the cyto D group contractile force continued to be reduced (13%+/-3%) and action potential characteristics did not show significant changes from control values after a 60-minute period of superfusion with cyto D-free Tyrode's solution.


CONCLUSIONS
We conclude that cyto D should be considered an alternative excitation-contraction uncoupler for optical mapping studies of cardiac repolarization.
Biermann
M
M
Krannert Institute of Cardiology, Indianapolis, Indiana 46202-4800, USA.
Rubart
M
M
Moreno
A
A
Wu
J
J
Josiah-Durant
A
A
Zipes
D P
DP
D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D015638:Cytochalasin D / Q000494:pharmacology*; D003931:Diacetyl / Q000031:analogs & derivatives* / Q000494:pharmacology; D004285:Dogs; D004594:Electrophysiology / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006321:Heart / Q000502:physiology*; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects*; D055095:Optics and Photonics; D012107:Research Design; D016276:Ventricular Function / Q000187:drug effects / Q000502:physiology
D004791:Enzyme Inhibitors; C004717:diacetylmonoxime; D015638:Cytochalasin D; D003931:Diacetyl