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 C and thereafter submitted to hypoxia were studied in different substrate 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 C 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 C and an increase for fishes acclimated to 30 degrees C.