The effect of hypoxia and recuperation on carbohydrate metabolism in pacu (Piaractus mesotamicus)

A study of the hematological parameters, glycogen, glucose, and lactate, and the activity of malate and lactate dehydrogenases was carried out in blood and tissues of fishes submitted to two, four, and six hours of hypoxia and recuperation. Only after 4 h of hypoxia was there a drop in liver glucose. After 6 h, a drop in lactate and a rise in glucose in practically all tissues signaled a recuperation of the metabolism, probably due to ASR (aerial surface respiration). Lactate formed during hypoxia was canalized to heart and brain for oxidation and used for neoglucogenesis. There were no changes in hematological parameters nore in the activity of malate and lactate dehydrogenases during normoxia and hypoxia, which suggest that these adaptive mechanisms may not be involved during hypoxia. Glycogen concentrations did not show variation during hypoxia either

Changes in lactate dehydrogenase and malate dehydrogenase activities during hypoxia and after temperature acclimation in the armored fish, Rhinelepis strigosa (Siluriformes, Loricariidae)

Lactate (LDH) and malate dehydrogenase (MDH) of white skeletal muscle of fishes acclimated to 20, 25 and 30 degrees Celsius and thereafter submitted to hypoxia were studied in different sbstrate concentrations. Significant differences for LDH and MDH of white muscle enzyme activities are described here for the first time in Rhinelepis strigosa of fishes acclimated to 20 degrees Celsius and submitted to hypoxia for six hours. LDH presented a significant decrease in enzyme affinity for pyruvate in acute hypoxia, for fishes acclimated to 20 degrees Celsius and an increase for fishes acclimated to 30 degrees Celsius.