Abstract
The distribution of glutamine synthetase (GS) was studied in rat retinas from the day of birth to adulthood by means of immunohistochemistry. GS was present in the pigment epithelium in the newborn rat, and over the next few days it was demonstrated around blood vessels and within small glial cells. The enzyme was first detected in perikarya and processes of Müller cells on day 5. The adult GS pattern was acquired by day 12, except for persistence of GS in the pigment epithelium. GS in the pigment epithelium gradually diminished to trace amounts between day 12 and 2 months. Additionally, GS was found in the inner epithelium of the ciliary body and posterior epithelium of the iris during the developmental period and in adults. Our results indicate that the dramatic rise in retinal GS biochemically demonstrated by other workers occurs exclusively in Müller cells. Moreover, the complete acquisition of GS in rat retina corresponds chronologically with certain maturational events including the onset of the electroretinographic response. The role of GS in the pigment epithelium and extraretinal structures is uncertain but it may denote their involvement in mucopolysaccharide metabolism.
