Anaerobic metabolism of the common cockle, Cardium edule—IV. Time dependent changes of metabolites in the foot and gill tissue induced by anoxia and electrical stimulation

Abstract

1. 1. The levels of adenylates, arginine phosphate, arginine and various other metabolites related to anaerobic metabolism were determined in foot and gills of Cardium edule during anoxia (incubation in oxygen-free sea water) up to 48 hr and after electrical stimulation of the foot muscle. 2. 2. In the foot the phosphagen was depleted quite rapidly in the first hours of anoxia. Free arginine levels rose while there was little octopine accumulation. d-Lactate appeared to be the predominant end product. Alanine and succinate were also produced and the concentration of aspartate decreased, suggesting this metabolite as precursor for succinate. In the gills, where no arginine phosphate was present, succinate production was higher than in the foot and exceeded lactate formation. 3. 3. Only a small decline in ATP occurred during anoxia and consequently, only moderate changes in the energy charge were observed in both tissues. 4. 4. Electrical stimulation of the foot also resulted in the breakdown of arginine phosphate and formation of mainly lactate and not octopine. 5. 5. Total ATP consumption during anoxia has been calculated to be more rapid during the first hours. The ATP consumption rate was reduced by a factor of 7.8 during 48 hr of anoxia. 6. 6. During the first 4 hr of anoxia about 60% of the total consumed energy (as ATP equivalents) was provided by the phosphagen, while later glycolysis contributed about 80%. During electrical stimulation about 75% of the energy supplied was derived from the phosphagen. 7. 7. A comparison of the C. edule results with the data during anoxia and exercise of the jumping cockle is made.