Lowering Extracellular pH Raises Intracellular Calcium in Cultured Rat Astrocytes

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The relationship between extracellular pH and intracellular calcium concentration ([Ca²⁺] ₁) in primary culture of neonatal rat astrocytes with Ca²⁺-indicator dye indo-1/acetoxymethyl ester and a confocal microscope was investigated. In 65 of 86 astrocytes studied, lowering extracellular pH by changing the perfusate solution from pH 7.4 to 6.4 was followed by increases in [Ca²⁺] ₁ in cytoplasm. The increases in [Ca²⁺] ₁ were seen on stimulation and/or during reperfusion. Of all the cells, 45.4% showed a transient pattern and 30.2% manifested a sustained pattern. The results suggest that a short interval but excessive acidic stimulation may be one of the signals that raises [Ca²⁺] ₁ in a certain population of cerebral astrocytes.