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Reversible decreases in ATP and PCr concentrations in anoxic turtle brain
Authors:L Buck  M Espanol  L Litt  P Bickler
Institution:aUniversity of Toronto, Department of Zoology, 25 Harbord Street, Toronto, Ont. M5S 3G5, Canada;bUniversity of California, Department of Anesthesia, 521 Parnassus Avenue, San Francisco, CA 94143-0542, USA
Abstract: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 become more acidic and cellular energy demands are met by anaerobic glycolysis. Because changes in adenylates and pH during anoxic stress could represent important signals triggering metabolic and ion channel down-regulation we measured PCr, ATP and intracellular pH in turtle brain sheets throughout a 3-h anoxic-re-oxygenation transition with 31P NMR. Within 30 min of anoxia, PCr levels decrease 40% and remain at this 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-oxygenation PCr, ATP and intracellular pH recover to pre-anoxic levels within 60 min. This is the first demonstration of a sustained reversible decrease in ATP levels with anoxia in turtle brain. The observed changes in pH and adenylates, and a probable concomitant increase in adenosine, may represent important metabolic signals during anoxia.
Keywords:31P NMR  pH  Chrysemys picta bellii  Western painted turtle  Anoxia tolerance  Adenylates  Perfused brain slice
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