BRAIN NA+ K+-ATPASE ACTIVITY IN 2 ANOXIA TOLERANT VERTEBRATES - CRUCIAN CARP AND FRESH-WATER TURTLE/

The crucian carp (Carassius carassius) and freshwater turtles (Trachem ys scripta) are among the very few vertebrates that can survive extend ed periods of anoxia. The major problem for an anoxic brain is energy deficiency. In the brain, the Na+/K+-ATPase is the single most ATP con suming enzyme, being responsible for maintaining ion gradients. We her e show that the Na+/K+-ATPase activity in the turtle brain is reduced by 31% in telencephalon and by 34% in cerebellum after 24 h of anoxia. Both changes were reversed upon reoxygenation. By contrast, the Na+/K +-ATPase activities were maintained in the anoxic crucian carp brain. These results support the notion that crucian carp and turtles use div ergent strategies for anoxic survival. The fall in Na+/K+-ATPase activ ities displayed by the turtle is likely to be related to the strong de pression of brain electric and metabolic activity utilized as an anoxi c survival strategy by this species. (C) 1997 Elsevier Science Ireland Ltd.