Cardiac force and high-energy phosphates under metabolic inhibition in four ectothermic vertebrates.
Isometric twitch tension of ventricular preparations stimulated at 0.2 Hz fell over 30 min of anoxia by a fraction decreasing in the order rainbow trout, cod, eel, and freshwater turtle. Drops in the estimated cytoplasmic energy state were related to larger tension losses for trout than for the other species, possibly due to larger changes in free phosphate. Anoxic energy degradation was slower for turtle than for the other species. Anoxia combined with glycolytic inhibition (1 mmol/l iodoacetate) enhanced the decrease in twitch tension for a drop in energy state and enlarged the increase in ADP/ATP relative to that in creatine/phosphocreatine to an extent inversely related to the creatine kinase activity. Furthermore, it increased resting tension to an extent possibly related to myosin-adenosinetriphosphatase (ATPase) activity and lowered the content of phosphorylated adenylates in trout and turtle myocardium. The results indicate that species differences in performance of the metabolically challenged myocardium depend on energy-degrading processes, e.g., myosin-ATPase activity, phosphate release, creatine kinase activity, and efflux/degradation of ADP and AMP, and that glycolysis offers protection due to its cytoplasmic localization.
Institute of Biological Sciences, University of Aarhus, Denmark.
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Hartmund
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Gesser
D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003401:Creatine / Q000378:metabolism; D003402:Creatine Kinase / Q000378:metabolism; D004524:Eels / Q000378:metabolism / Q000502:physiology*; D004734:Energy Metabolism; D005399:Fishes / Q000378:metabolism / Q000502:physiology*; D000860:Hypoxia / Q000378:metabolism; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D009200:Myocardial Contraction; D009218:Myosins / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism / Q000502:physiology; D010710:Phosphates / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D014426:Turtles / Q000378:metabolism / Q000502:physiology*
D007461:Iodoacetates; D010710:Phosphates; D010725:Phosphocreatine; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003402:Creatine Kinase; D009218:Myosins; D003401:Creatine; D019807:Iodoacetic Acid