Fructose-1,6-bisphosphate stabilizes brain intracellular calcium during hypoxia in rats.
BACKGROUND AND PURPOSE: Exogenously administered fructose-1,6-bisphosphate reduces neuronal injury from hypoxic or ischemic brain insults. To test the hypothesis that fructose-1,6-bisphosphate prevents changes in intracellular calcium ([Ca2+]i) and high-energy phosphate levels, we measured [Ca2+]i, intracellular pH (pHi), and adenosine triphosphate in cultured rat cortical astrocytes and cortical brain slices during hypoxia. METHODS: The fluorescent indicators fura-2 and bis-carboxyethyl-carboxyfluorescein were used to simultaneously measure [Ca2+]i and pHi with a fluorometer. RESULTS: Exposure to hypoxia (95% N2, 5% CO2) or 100 microM sodium cyanide produced transient increases in [Ca2+]i in astrocytes and sustained increases in [Ca2+]i in brain slices. Adenosine triphosphate levels fell in slices exposed to hypoxia or cyanide. Fructose-1,6-bisphosphate (3.5 mM) blocked increases in [Ca2+]i and prevented depletion of adenosine triphosphate. Fructose-1,6-bisphosphate also partially prevented adenosine triphosphate depletion in brain slices incubated in glucose-free medium. Iodoacetate (a specific inhibitor of glycolysis) elevated [Ca2+]i and partially prevented these actions of fructose-1,6-bisphosphate. Changes in pHi during hypoxia were not affected by fructose-1,6-bisphosphate. CONCLUSIONS: Fructose-1,6-bisphosphate supports adenosine triphosphate production via stimulation of glycolysis and results in the maintenance of normal [Ca2+]i during hypoxia or hypoglycemia.[1]References
- Fructose-1,6-bisphosphate stabilizes brain intracellular calcium during hypoxia in rats. Bickler, P.E., Kelleher, J.A. Stroke (1992) [Pubmed]
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