ATP-Induced Oscillations of Cytosolic Ca2+ Activity in Cultured Astrocytes from Rat Brain are Modulated by Medium Osmolarity Indicating a Control of [Ca2+]i Oscillations by Cell Volume |
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Authors: | Reetz G Wiesinger H Reiser G |
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Institution: | (1) Institut für Neurobiochemie Medizinische Fakultät der Otto-von-Guericke-Universität Magdeburg, Leipziger Straße 44, 39120 Magdeburg, Germany;(2) Physiologisch-Chemisches Institut Universität Tübingen, Tübingen, Germany;(3) Present address: Abteilung Vergleichende Neurobiologie, Universität Ulm, 89069 Ulm, Germany |
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Abstract: | Oscillations of cytosolic Ca2+ activity (Ca2+]i) induced by stimulation with ATP in rat astrocytes in primary cultures were analysed. Astrocytes, prepared from the brains of newborn rats, loaded with the fluorescent Ca2+ indicator fura-2/AM, were continuously stimulated with ATP (10 M). ATP caused a large initial Ca2+ peak, followed by regular Ca2+]i oscillations (frequencies 1–5/min). Astrocytes were identified by glial fibrillary acidic protein staining of cells after Ca2+]i recording. The oscillations were reversibly blocked by the P2 purinoceptor antagonist suramin (30 M). Influx of extracellular Ca2+ and mobilization of Ca2+ from intracellular stores both contributed to the oscillations. The effects of hypertonic and hypotonic superfusion medium on ATP-induced Ca2+]i oscillations were examined. Hypertonic medium (430 mOsm) reversibly suppressed the ATP-induced oscillations. Hypotonic medium (250 mOsm), in spite of having heterogeneous effects, most frequently induced a rise in Ca2+]i, or reversibly increased the frequency of the oscillations. Thus, a change in cell volume might be closely connected with Ca2+]i oscillations in astrocytes indicating that Ca2+]i oscillations in glial cells play an important role in regulatory volume regulation in the brain. |
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Keywords: | Astroglia primary culture purinoceptors Ca2+ oscillations cell volume |
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