L-Glutamate-induced swelling of cultured astrocytes is dependent on extracellular Ca 2+

Abstract

l-Glutamate ( l-Glu)-induced swelling of astrocyte cultures from rat brain was examined by determining [ 3 H]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 Ca 2+-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 Ca 2+. These results indicate that swelling of astrocytes induced by l-Glu is characterized by an accompanied influx of Ca 2+.