L-glutamate-induced swelling of cultured astrocytes is dependent on extracellular Ca2+

L-Glutamate (L-Glu)-induced swelling of astrocyte cultures from rat brain was examined by determining [3H]O-methyl-D-glucose ([3H]OMG) uptake. Time-course of the L-Glu (0.5 mM)-induced increase in [3H]OMG space of astrocytes showed two phases; about 30% increase was obtained in 10 min and the increased [3H]OMG space was steady up to 20 min. Then, the [3H]OMG space was further increased during the incubations longer than 30 min. In Ca2(+)-free conditions, while the time-course up to 20 min was similar to that in the normal condition, the increase in [3H]OMG space by further incubations was not shown. The L-Glu-increased [3H]OMG space persisted for 2 h in a L-Glu-free medium and thereafter turned to the normal level in 4 h. In contrast, the incubation in a L-Glu-free medium for 30 min reversed the increased [3H]OMG space in the absence of extracellular Ca2+. These results indicate that swelling of astrocytes induced by L-Glu is characterized by an accompanied influx of Ca2+.