REVERSIBLE DECREASES IN ATP AND PCR CONCENTRATIONS IN ANOXIC TURTLE BRAIN

A hallmark of anoxia tolerance in western painted turtles is relative constancy of tissue adenylate concentrations during periods of oxygen limitation. During anoxia heart and brain intracellular compartments b ecome more acidic and cellular energy demands are met by anaerobic gly colysis. Because changes in adenylates and pH during anoxic stress cou ld represent important signals triggering metabolic and ion channel do wn-regulation we measured PCr, ATP and intracellular pH in turtle brai n sheets throughout a 3-h anoxic-re-oxygenation transition with P-31 N MR. Within 30 min of anoxia, PCr levels decrease 40% and remain at thi s level during anoxia. A different profile is observed for ATP, with a statistically significant decrease of 23% occurring gradually during 110 min of anoxic perfusion. Intracellular pH decreases significantly with the onset of anoxia, from 7.2 to 6.6 within 50 min. Upon re-oxyge nation PCr, ATP and intracellular pH recover to pre-anoxic levels with in 60 min. This is the first demonstration of a sustained reversible d ecrease in ATP levels with anoxia in turtle brain. The observed change s in pH and adenylates, and a probable concomitant increase in adenosi ne, may represent important metabolic signals during anoxia. (C) 1998 Elsevier Science Inc. All rights reserved.