RECOVERY OF THE ENERGY-METABOLISM AFTER A HYPOXIC CHALLENGE AT DIFFERENT TEMPERATURE CONDITIONS - A P-31-NUCLEAR MAGNETIC-RESONANCE SPECTROSCOPY STUDY WITH COMMON CARP

We determined the effects of a mild hypoxic challenge on the energy me tabolism of the common carp, Cyprinus carpio, under different temperat ure conditions, by P-31-nuclear magnetic resonance spectroscopy (P-31- NMR). Fish were acclimated to the optimal temperature of 25 degrees C or the acute sublethal temperature of 33 degrees C. A group of the 25 degrees C acclimated fish was also exposed to a temperature shock of 3 3 degrees C. The resting levels of phosphocreatine (PCr) and inorganic phosphate (P-i) were comparable between the three groups. The level o f ATP remained unchanged under all experimental conditions. Submission to a short hypoxic challenge resulted in acidosis and a depletion of PCr, while Pi increased. The recovery of the PCr levels after hypoxia was independent of the temperature to which the fish were acclimated, but when submitted to an acute temperature shock, the recovery was muc h slower. Resting intracellular pH (pH(i)) decreased under increasing temperature and the recovery of pH, was independent of the temperature condition. The extent of acidosis under the hypoxic challenge was mor e severe in carp exposed to both the acute and the chronic sublethal t emperature stress. This study revealed that shortly after exposure to a sublethal acute temperature stress, significant differences in the c apacity to recover from an hypoxic challenge had occurred. After a per iod of 4 weeks exposure to a sustained sublethal high temperature, car p regain the capacity to recover fully from the hypoxia, indicating th at acclimation had occurred. (C) 1998 Elsevier Science Inc. All rights reserved.