Background:Nitric oxide(NO)plays a significant role in physiological and pathological processes in the retina.In the Larginine-NO pathway,NO synthase(NOS)converts L-arginine to NO and L-citrulline.Increased NO production,mediated by inducible NOS has been implicated in the pathogenesis of various vitreoretinal diseases.In the present study it is hypothesized that in rhegmatogenous retinal detachment(RRD),the production of NO pathway metabolites might be upregulated.Methods:Using high-pressure liquid chromatography citrulline,arginine and nitrite were measured in vitreous fluid of 93 eyes with RRD,nine eyes with a traction retinal detachment due to proliferative diabetic retinopathy(PDR),and in 49 control samples of vitreous fluid from eyes without retinal detachment.Results:The mean vitreous concentrations of citrulline and arginine were significantly increased in eyes with RRD(9.6± 4.3 and 97.3± 29.2;respectively)or in eyes with a traction retinal detachment(25.8± 10.3 and 130.7± 23.7;respectively)as compared to control eyes(7.1± 3.2 and 75.9± 18.1;respectively).The mean level of nitrite was also higher in vitreous fluid of patients with RRD(2.24± 1.4)or patients with a traction retinal detachment(2.21± 0.72)than in the controls(2.01± 0.72),although not significantly so.Conclusions:We found increased levels of NO pathway metabolites in the vitreous fluid of eyes with retinal detachment,which may reflect a possible role of NO in the pathogenesis of this disease. Background: Nitric oxide (NO) plays a significant role in physiological and pathological processes in the retina.In the Larginine-NO pathway, NO synthase (NOS) converts L-arginine to NO and L-citrulline. Increased NO production, mediated by inductivity NOS has been implicated in the pathogenesis of various vitretinal diseases. In the present study it is hypothesized that in rhegmatogenous retinal detachment (RRD), the production of NO pathway metabolites might be upregulated. Methods: Using high-pressure liquid chromatography citrulline, arginine and nitrite were measured in vitreous fluid of 93 eyes with RRD, nine eyes with a traction retinal detachment due to proliferative diabetic retinopathy (PDR), and in 49 control samples of vitreous fluid from eyes without retinal detachment. Results: The mean vitreous concentrations of citrulline and arginine were significantly increased in eyes with RRD (9.6 ± 4.3 and 97.3 ± 29.2; respectively) or in eyes with a traction retinal detachment (25.8 ± 10.3 and 130.7 ± 23.7; respectively) as compared to control eyes (7.1 ± 3.2 and 75.9 ± 18.1; respectively). The mean level of nitrite was also higher in vitreous fluid of patients with RRD (2.24 ± 1.4) or patients with a traction retinal detachment ± 0.72) than in the controls (2.01 ± 0.72), although not significantly so. Conlusions: We found increased levels of NO pathway metabolites in the vitreous fluid of eyes with retinal detachment, which may reflect a possible role of NO in the pathogenesis of this disease.