Dependence of cerebral energy phosphate and evoked potential recovery on end-ischemic pH

P. D. Hurn, R. C. Koehler, S. E. Norris, K. K. Blizzard, R. J. Traystman

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

We determined whether the rate of metabolic recovery and electrophysiological deficit after incomplete cerebral ischemia is related to intracellular pH (pH(i)) achieved at the end of ischemia in a dose-dependent manner. End-ischemic pH(i) was varied by employing two ischemic durations, 12 and 30 min, and by setting preischemic plasma glucose to ~80 or 400 mg/dl. Incomplete global ischemia was produced in anesthetized dogs by transient intracranial hypertension followed by 4 h of reperfusion, and pH(i), ATP, and phosphocreatine (PCr) were measured with 31P magnetic resonance spectroscopy. Cerebral blood flow was reduced to ~6 ml·min-1·100 g-1 during ischemia. End-ischemic pH(i) was >5.7 in all animals from various treatment groups except for four of seven dogs treated with 30-min hyperglycemic ischemia. When end-ischemic pH(i) remained >5.7, there was nearly complete recovery of ATP, PCr, pH(i), intracellular bicarbonate concentration ([HCO3-](i)), and O2 consumption. Partial recovery of somatosensory-evoked potentials (SEP) occurred in most of these animals. In the 30-min hyperglycemic animals in which pH(i) fell below 5.5, ATP, PCr, and O2 consumption recovered by only one-half over 60 min of reperfusion and then declined to near-zero levels without SEP recovery. In addition, pH(i) remained <6.0, and [HCO3-](i) remained <2 mM throughout reperfusion. We conclude that there is an apparent in vivo pH(i) threshold of ~5.5-5.7 during incomplete cerebral ischemia that is associated with an inability to significantly restore pH(i) and [HCO3-](i) and with secondary deterioration of high-energy phosphate levels.

Original languageEnglish (US)
Pages (from-to)H532-H541
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume260
Issue number2 29-2
DOIs
StatePublished - 1991

Keywords

  • Adenosine triphosphate
  • Bicarbonate ion
  • Cerebral blood flow
  • Cerebral oxygen consumption
  • Hyperglycemia
  • Magnetic resonance spectroscopy
  • Somatosensory-evoked potential

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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