Objective To investigate the expression of aquaporin (AQP)1 in retina during neovascularization.Methods Sixty C57BL/6J 7-day-old mice were randomly divided into 2 equal groups.The 30 mice of the model group were raised in 75%±2%oxygen for 5 days and then returned to condition with normal oxygen (room air) for 3-5 days.12,15,and 17 days after birth (on the postnatal day 12,15,and 17)10 mice from each group were kiUed respectively.Immunohistochemistry was used on 6 eyes and RT-PCR and Western blotting were used to detect the mRNA and protein expression of AQP1 in 7 eyes respectively.Thirty mice were raised in normal oxygen as controls.Results The retinal neovagcularization rate on P17 in the model group was 100%.AQP1 expression in retina was seen in 1 eye from the model and control groups each on P12,and in all mice of both groups on P15 and P17,especially in the lateral retina.AQP1 expression in retinal endothelial cells was seen in the model mice and not in the control mice.There were not significant differences in the AQPl mRNA expression level on P12 and P15 between the 2 groups,however.the AQPl mRNA expression level on P17 was significantly higher in the model group than in the control group(1.81±1.02 vs 1.15-4-0.01,P=0.000).AQP1 protein expression was seen on P12,P15,and P17 in both groups,and the AQP1 protein expression level at P17 of the model group was significantly higher than that of the control group(1.82±0.05 vs 1.57±0.04,p=0.000).Conclusion AQP1 protein may play an important role in retinal neovascularization.