Induction of glutamine synthetase in embryonic neural retina: localization in Müller fibers and dependence on cell interactions.

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Abstract
The cellular localization of glutamine synthetase [GSase] induced by cortisol in the neural retina of chicken embryos was investigated by immunostaining with GSase-specific antiserum and indirect immunofluorescence. In organ cultures of retina tissue, and in the retina in vivo, hormone-induced GSase was found to be confined only to the Mueller fibers (retinoglia). In mature chicken retina, which contains a very high level of GSase, the enzyme was detected solely in Mueller fibers. In short-term monolayer cultures of dispersed embryonic retina cells, there was no GSase induction and no immunodetectable increase in enzyme level. When the dispersed cells were reaggregated and they restituted retinotypic cell associations, GSase could be induced and it was localized in Mueller fibers. In addition to the horminal stimulus, contact-dependent interactions between Mueller glia cells and retina neurons are involved in the mechanism of GSase induction in the retina.