GLAST expression on bullfrog Müller cells is regulated by dark/light

Using immunofluorescence double-labeling, Western blotting and confocal laser scanning microscopy, we investigated if and how the expression of glial high-affinity glutamate/aspartate transporter (GLAST) in bullfrog Müller cells may be regulated by dark/light. Compared with light-adapted retinas, the expression of GLAST in Müller cells was overall up-regulated in retinas dark-adapted for 30 min but declined in retinas dark-adapted for longer (>30 min) periods. The declined expression level of GLAST during prolonged dark adaptation was raised by immersion with 1 mM glutamate. These results suggest that glutamate uptake mediated by GLAST could be regulated dynamically and efficiently in accord with dark/light-induced changes in glutamate release of retinal neurons.