·AIM:To observe the inhibitory effect of melatonin(MLT)on cataractous lenses of rabbits induced by high glucose.METHODS:The lenses of the cultured normal rabbits in vitro were randomly divided into 3 groups:the control group(group A),the group treated by high glucose(group B),and the group treated by high glucose and MLT in 50μmol/L(group C).The effect of the drug was observed at different time points(48 hours,72 hours,96 hours).At the same time,superoxide dismutase(SOD),catalase(CAT)and malondialdehyde(MDA)were tested.RESULTS:The observation of lenses after 96 hours culture,lenses in group A were transparent.The opacity in rabbits group C was apparently lower than that of in group B.The measurement of biochemical indicator of lenses:the levels of SOD and CAT were increased significantly in group C compared with that of group B(P<0.01).The level of MDA was significantly decreased compared with that of group B(P<0.01).CONCLUSION:MLT plays an inhibitory role in high glucose induced rabbit lens oxidation injury and can delay and ameliorate the occurrence and development of diabetic cataract.