Anaerobic energy metabolism of the European eel,Anguilla anguilla L.

Abstract

Eels, acclimated the 15°C and aerated water (PO2 130 mm Hg) were exposed to hypoxia (PO2 lowered from 130 to 8 mm Hg in 4 h) and to complete anoxia until loss of equilibrium. Experiments were carried out at night. The mean survival time (LT50) during anoxic conditions proved to be 5.7 h. ATP, ADP, AMP, IMP, CrP, glycogen, lactate, pyruvate, α-ketoglutarate, malate, succinate, alanine, aspartate, glutamate and ammonia levels were determined in skeletal muscle and liver of control, hypoxic and anoxic fish. Some of the mentioned parameters were also measured in heart muscle and blood. Hypoxia causes declines of aspartate (muscle), CrP (muscle) and glycogen (liver, heart), and increases of alanine (blood, liver) and lactate (blood, liver, heart). During anoxia, muscle CrP stores are almost completely exhausted and adenylates are partially broken down to IMP. A decrease of glycogen and an accumulation of lactate were observed in all tissues examined. The energy charge of muscle and heart did not drop below 0.79, but in liver tissue it decreased from 0.65 to 0.17. Liver cytoplasm became significantly reduced during anoxia, but such a change of redox state did not occur in muscle. Eels seem to lack the capacity for anaerobic fermentation of glycogen to ethanol, as observed in goldfish. Lactate glycolysis and creatine phosphate breakdown appear to be the main energy producing pathways during anaerobiosis.