Extracellular alkalinity exacerbates injury of cultured cortical neurons.
OBJECTIVE
We have previously shown that extracellular acidity protects cultured fetal murine neocortical neurons from glutamate toxicity and combined oxygen-glucose deprivation injury, an action at least in part mediated by reduction in N-methyl-D-aspartate receptor activation. We now investigate the effect of extracellular alkalinity on both glutamate neurotoxicity and injury due to combined oxygen-glucose deprivation.


METHODS
The effects of extracellular alkalinity during injury induced by exposure of murine neocortical cultures to glutamate (0.5 mM for 5 minutes) or oxygen-glucose deprivation are characterized morphologically and quantitated by efflux of lactate dehydrogenase from both neurons and glia to the bathing medium. Calcium accumulation is measured with calcium-45.


RESULTS
Moderate extracellular alkalinity is well tolerated by cortical cells but significantly potentiates both glutamate neuronal toxicity and oxygen-glucose deprivation neuronal injury. In contrast, glial viability in the face of combined oxygen-glucose deprivation is little affected by extracellular alkalinity. Increased accumulation of calcium-45 during oxygen-glucose deprivation in alkalotic medium and blockade of this increase by MK-801 is demonstrated.


CONCLUSIONS
These observations suggest that alkaline pH can exacerbate excitotoxic neuronal injury, most likely because of increased N-methyl-D-aspartate receptor activation. Metabolic alkalosis of any etiology may sensitize neurons to ischemic injury and potentiate reperfusion injury.
Giffard
R G
RG
Department of Anesthesia, Stanford University School of Medicine, Calif. 94305-5117.
Weiss
J H
JH
Choi
D W
DW
D000468:Alkalies / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism* / Q000473:pathology; D005110:Extracellular Space / Q000378:metabolism*; D005947:Glucose / Q000172:deficiency; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000473:pathology; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology
D000468:Alkalies; D005971:Glutamates; D018698:Glutamic Acid; D005947:Glucose; D002118:Calcium