[L-arginine in the lacrimal fluid of patients with diabetic retinopathy and the possible role of nitric oxide in the pathogenesis of retinal ischemia].

The concentrations of 23 free amino acids and some other components (ammonium, urea, ethanolamine) were measured by liquid chromatography in the lacrimal fluid of 40 patients with diabetic retinopathy (DR) (15 with the preproliferative stage and 25 with proliferative stage) and 15 normal subjects. The mean level of L-arginine in DR patients was 3.5-5 times decreased in comparison with the control (1.2 +/- 0.4 vs. 6.1 +/- 1.5%, p < 0.005). The level of ornithine inversely correlated with the level of L-arginine. The mean level of ornithine in DR patients was increased twofold (12.3 +/- 1.0 vs 6.8 +/- 1.0% in the control, p < 0.005). The mean concentrations of other amino acids virtually did not change. Decreased level of L-arginine in the lacrimal fluid of DR patients may be indicative of increased utilization of this amino acid in retinal ischemia, which, according to the modern concept of DR pathogenesis, can be caused by activation of nitric oxide production. Measurement of L-arginine in the lacrimal fluid can serve as a simple noninvasive and reliable method for early diagnosis of ischemic changes in the retina.