Abstract: Objective To explore the effect of taurine on the expression of nitric oxide(NO)and nitric oxide synthase(NOS)indiabeticratretina.Methods Arat model of diabetic retinop a thy(DR)was induced by intrape ritoneal injection of streptozotoc in(S TZ).Twenty-four adultmale Sprague-Dewley rats were randomly divided into three groups:normal control guoup,diabetic guoup,taurine-treated diabetic group(dietary supplementation with 1.2% taurine).The rats were sacrificed at the time of 12 weeks.The content of NO in retina was detected with nitrate reduc tase method.The distribution and changes of neuronal nitric oxide synthase(nNOS)and inducible nitric oxide synthase(iNOS)were studied with immunoh is tochemical localization.Results The content of NO indiabetic guoup and taurine-treated diabetic guoup was 2.138±0.260 and 1.053±0.159μmol/L,respectively.The difference was statistically significant(P<0.01).Mean absorbance of iNOS was markedly lower in taurine-treated diabetic guoup than in diabetic guoup(0.101±0.006 vs 0.390±0.022,P<0.01).However,mean absorbance of nNOS was significantly higher in taurine-treated diabetic guoup than in diabetic guoup(0.429±0.035 vs.0.125±0.024,P<0.01).Conclusion Tau rine supp lementationame lioratesdiabe tic retinop a thy via down regulating NO and influencing the expression of iNOS and nNOS in rats.