Objective To observe the changes of expression of glutamine synthetase (GS) in early diabetic ratsprime; retina and investigate its possible mechanism. Methods Three groups of streptozotocininduced diabetic models of SpragueDawley (SD) rats with different diseased courses, ie, 1 month, 2 months, and 3 months, respectively, with 8 rats in each group, and 8 normal ones as control were examined. The expressions of GS, interleukin-1beta; (IL-1beta;) and c-Jun in retina in the 4 groups were detected by indirect immunofluorescence and western blotting techniques. Meanwhile, different doses of IL-1beta;（0,100,500,and 1000 ng/ml） were injected into the vitreous cavities of 32 normal rats (8 rats in each group), and 24 hours later, the expressions of GS and c-Jun in retina were detected by the same methods. Results The expression of GS in retina did not changed in control group or in 1 month and 2 months group, but decreased obviously in 3 months group comparing with which in the control group (Plt;0.01).The expressions of c-Jun and IL-1beta; in retina in control group were very low, but increased gradually in diabetic rats in 1-3 months group, which significantly differed from which in the control group (Plt;0.01). Vitreous injection with IL-1beta; (500 and 1000 ng/ml) down regulated the expressions of GS, and the expression of c-Jun increased in a dose-dependent way after injection with IL-1beta; at the concentration of 100 ng/ml. Conclusions In early diabetic ratsrsquo; retina, IL-1beta; may down regulate the expression of GS. The possible mechanism may be the activation of c-Jun by IL-1beta;. (Chin J Ocul Fundus Dis,2007,23:260-264)