title: Nitric oxide and vascular endothelial growth factor concentrations are increased but not related in vitreous fluid of patients with proliferative diabetic retinopathy.
abstract: OBJECTIVE
  Several reports have implicated nitric oxide (NO) in the angiogenic process. The assessment of NO stable end products, nitrite and nitrate (NOx), is commonly used as a measure of NO production in biological fluids. The aims of the study were to investigate NOx concentrations in the vitreous fluid of patients with proliferative diabetic retinopathy (PDR) and to evaluate the relationship between NOx and vascular endothelial growth factor (VEGF).
  
  
  METHODS
  Serum and vitreous fluid samples were obtained simultaneously at the time of vitreoretinal surgery from 23 patients with PDR, and 17 control non-diabetic patients with non-proliferative ocular disease. NOx was determined by using the Griess reaction and VEGF levels were assessed by ELISA.
  
  
  RESULTS
  The intravitreous concentration of NOx was significantly elevated in patients with PDR in comparison with the control group (31.6 +/- 2.96 micromol/l vs. 18 +/- 2.46 micromol/l; P = 0.01). However, we did not detect any differences between NOx serum concentrations. We observed a correlation between serum and vitreous levels of NOx in diabetic patients (r = 0.79; P < 0.001), but not in the control group. Intravitreous levels of VEGF in patients with PDR were higher than those obtained in serum (1.42 ng/ml (0.12-7.62) vs. 0.12 ng/ml (0.03-0.42); P < 0.01). Vitreal levels of VEGF were strikingly higher in patients with PDR than in the control subjects (1.42 ng/ml (0.12-7.62) vs. 0.009 ng/ml (0.009-0.04); P < 0.001). No correlation between vitreal concentrations of NOx and VEGF was observed, either in diabetic patients or in the control group.
  
  
  CONCLUSIONS
  NOx and VEGF are increased but not related in the vitreous fluid of diabetic patients with PDR. Our results suggest that serum diffusion could play a significant role in explaining the increase of NOx. By contrast, intraocular production seems to be the main factor responsible for the intravitreous enhancement of VEGF.
authors.affiliation: Diabetes Unit, Endocrinology Division, Hospital General Universitari Vall d'Hebron, Pg. Vall d'Hebron 119-129, 08035 Barcelona, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Hernández
authors.forename: A
authors.initials: A
authors.lastname: Lecube
authors.forename: R M
authors.initials: RM
authors.lastname: Segura
authors.forename: L
authors.initials: L
authors.lastname: Sararols
authors.forename: R
authors.initials: R
authors.lastname: Simó
mesh_terms: D003922:Diabetes Mellitus, Type 1 / Q000209:etiology / Q000378:metabolism*; D003930:Diabetic Retinopathy / Q000209:etiology / Q000378:metabolism*; D016228:Endothelial Growth Factors / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D008222:Lymphokines / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D014822:Vitreous Body / Q000737:chemistry*
chemical_list: D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D009569:Nitric Oxide