Using cultured rat retinal glial cells, the changes in the expression of glutamate transporters (GLTs) under such conditions as the degree of confluence of the cells, hypoxia, glutamate loading, and potassium loading, were assessed. After the retinal glial cells were isolated from 3-day-old Sprague-Dawley rats, GLAST, GLT-1, and EAAC1 mRNA expression was confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and their protein expression was confirmed by Western blot analysis and immunostaining. Changes in the expression of the GLTs at 6 h after passage and at confluence, during culture in 5% oxygen, during glutamate loading and during potassium loading were assessed using real-time PCR. Although the GLAST mRNA expression was increased during glutamate and potassium loading, no changes in the expression were observed during hypoxia and at confluence. By contrast, the GLT-1 mRNA expression was increased during hypoxia and at confluence, but not during glutamate and potassium loading, and the EAAC1 mRNA expression was not changed only during glutamate loading. The expression of EAAC1 in the cultured retinal glial cells was confirmed. The expression of the GLTs varied according to the environment and the type of load suggests that the involvement of the GLTs in retinal physiology and pathology varies depending on the subtype.