Effects of metabolic inhibition on conduction, Ca transients, and arrhythmia vulnerability in embryonic mouse hearts.
Developing myocardium is more dependent on glycolysis than adult myocardium, yet the effects of selectively inhibiting glycolysis versus oxidative phosphorylation on embryonic heart function have not been well characterized. Accordingly, we investigated how selective metabolic inhibition affects membrane voltage and intracellular Ca (Ca(i)) transients in embryonic mouse hearts, including their susceptibility to arrhythmias. A total of 136 isolated embryonic mouse hearts were exposed to either 1) 2-deoxyglucose (2DG; 10 mM) or iodoacetate (IAA; 0.1 mM) with 10 mM pyruvate in place of glucose to selectively inhibit glycolysis or 2) the mitochondrial uncoupler protonophore carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP; 500 nM) with 10 mM glucose present to selectively inhibit oxidative phosphorylation. Using confocal imaging, we found that mitochondrial membrane potential monitored with tetramethylrhodamine methyl ester (200 nM) remained stable with 2DG or IAA but depolarized within 5 min after exposure to FCCP. IAA and FCCP decreased heart rate, inhibited Ca(i) transient amplitude, shortened action potential duration at 80% repolarization (APD(80)), and prolonged atrioventricular conduction time to similar extents. Although 2DG decreased heart rate and Ca(i) transient amplitude, it did not significantly affect APD(80) and AV conduction time. In addition, spontaneous arrhythmias occurred in 77 of 136 embryonic hearts (57%) after exposure to IAA (28/53) or FCCP (49/83). There were no significant differences in the types or incidence of arrhythmias induced by IAA and FCCP. These data support the idea that both glycolysis and oxidative phosphorylation play critical metabolic roles in regulating cardiac function in the embryonic mouse heart.
Cardiovascular Research Laboratory, David Geffen School of Medicine at University of California, Los Angeles, California 90095-1760, USA.
Fuhua
F
Chen
Carlos
C
De Diego
Lai-Hua
LH
Xie
Jun-Hai
JH
Yang
Thomas S
TS
Klitzner
James N
JN
Weiss
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology* / Q000633:toxicity; D001145:Arrhythmias, Cardiac / Q000139:chemically induced / Q000378:metabolism* / Q000503:physiopathology; D020013:Calcium Signaling / Q000187:drug effects*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D003847:Deoxyglucose / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology* / Q000633:toxicity; D006019:Glycolysis / Q000187:drug effects*; D006321:Heart / Q000187:drug effects* / Q000196:embryology; D006329:Heart Conduction System / Q000187:drug effects / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D007461:Iodoacetates / Q000494:pharmacology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D018613:Microscopy, Confocal; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D012508:Sarcolemma / Q000187:drug effects; D013997:Time Factors; D014475:Uncoupling Agents / Q000494:pharmacology
D000963:Antimetabolites; D004791:Enzyme Inhibitors; D007461:Iodoacetates; D014475:Uncoupling Agents; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D003847:Deoxyglucose