Release of glutamic acid from C6 glioma cells by extracellular glucose

Abstract

We already reported that glutamic acid was released from C6 glioma cells by the hypotonic challenge via the pathway distinct from Cl⁻ channels or glutamate transporters. Recently we found that glutamic acid was released from C6 glioma cells by the application of extracellular glucose. We measured the extracellular concentration of glutamic acid using the system we established before. The concentration of glutamic acid increased from ~4μM at the control condition in the absence of glucose to ~15μM by the application of the 5mM glucose. Application of mannitol, sucrose, lactose, or galactose did not show any increase of extracellular glutamic acid. Blockers of volume-sensitive Cl⁻ channel, including phloretin and arachidonic acid, did not block glucose-induced glutamic acid release from C6 cells. Gd³⁺, the blocker for ATP release from swollen cells, or inhibitors of glutamate transporters also failed to block glutamic acid release from C6 cells by extracellular glucose. These characteristics are quite similar with those of swelling-induced glutamic acid release. We conclude that glutamic acid is released from C6 cells by extracellular glucose possibly via the common membrane permeation pathway of swelling-induced glutamic acid release. [Jpn J Physiol 54 Suppl:S72 (2004)]