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.
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 microM). ATP caused a large initial [Ca2+]i 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 microM). 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.
Reetz
G
G
Institut für Neurobiochemie Medizinische Fakultät der Otto-von-Guericke-Universität Magdeburg, Germany.
Wiesinger
H
H
Reiser
G
G
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D007700:Kinetics; D009994:Osmolar Concentration; D051381:Rats; D017208:Rats, Wistar
D005456:Fluorescent Dyes; D005904:Glial Fibrillary Acidic Protein; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; C049925:fura-2-am; D000255:Adenosine Triphosphate; D002118:Calcium; D016257:Fura-2