Mechanical performance and glycolytic requirement in trout ventricular muscle

The glycolytic pathway seems to be coupled to the aerobic performance in mammalian cardiac muscle. Because many conditions are different in ectotherms, its influence on twitch force and resting force was recorded at 15 degrees C in isometric ventricular preparations from rainbow trout. To reduce glycolytic activity, preparations were exposed to 0.4 mmol l(-1) iodoacetate for 35 min or alternatively to 120 min anoxia in a glucose-free solution containing 10 mol l(-1) adrenaline in an attempt to remove glycolytic substrates. The anoxic period was followed by recovery in an oxygenated solution containing aerobic substrates but no glucose. Control experiments indicated that this treatment, like iodoacetate, inhibits glycolysis, although glycogen was reduced by one half only. In fully oxygenated preparations with access to mitochondrial substrates, both attempts to reduce glycolytic activity tended to increase both resting force and the reductions in twitch force during high activity imposed by high stimulation rates and exposure to 10 mol l(-1) adrenaline. Thus, the glycolytic pathway appears to be of specific importance under aerobic conditions also in the heart of ectotherms. J. Exp. Zool. 293:360-367, 2002.