title: Preserved Pressure Autoregulation but Disturbed Cyclo-Oxygenase and Nitric Oxide Effects on Retinal Arterioles during Acute Hypoxia in Diabetic Patients without Retinopathy.
abstract: BACKGROUND
  Acute hypoxia induces retinal vasodilatation, which depends on cyclooxygenase (COX) products and nitric oxide (NO) in vitro. However, it is unknown whether these mechanisms are active in diabetic patients and may contribute to the development of diabetic retinopathy.
  
  
  METHODS
  The Dynamic Vessel Analyzer was used to study the diameter regulation in retinal vessels during hypoxia in type 1 diabetic patients without retinopathy. The influence of NO and COX synthesis inhibition on the diameter of larger retinal vessels was studied during hypoxia, during isometric exercise and during flicker stimulation.
  
  
  RESULTS
  Increased arterial blood pressure during L-NMMA infusion and isometric exercise were paralleled by constriction of the retinal arterioles suggesting normal pressure autoregulation. Hypoxia significantly reduced the diameter responses during isometric exercise and during flicker stimulation as compared to normal persons.
  
  
  CONCLUSIONS
  The findings support that changes in metabolic autoregulation develop before changes in pressure autoregulation in diabetic patients.
authors.affiliation: Department of Ophthalmology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Line
authors.initials: L
authors.lastname: Petersen
authors.forename: Toke
authors.initials: T
authors.lastname: Bek
mesh_terms: D000328:Adult; D062186:Arterial Pressure / Q000502:physiology; D001160:Arterioles; D016861:Cyclooxygenase Inhibitors / Q000008:administration & dosage*; D003922:Diabetes Mellitus, Type 1 / Q000150:complications / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000209:etiology; D004008:Diclofenac / Q000008:administration & dosage; D045462:Endothelium-Dependent Relaxing Factors / Q000037:antagonists & inhibitors; D005260:Female; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009569:Nitric Oxide / Q000037:antagonists & inhibitors*; D011446:Prospective Studies; D012161:Retinal Artery / Q000503:physiopathology*; D014664:Vasodilation / Q000187:drug effects; D019323:omega-N-Methylarginine / Q000008:administration & dosage*
chemical_list: D016861:Cyclooxygenase Inhibitors; D045462:Endothelium-Dependent Relaxing Factors; D004008:Diclofenac; D019323:omega-N-Methylarginine; D009569:Nitric Oxide