title: Purinergic mechanisms and prostaglandin E receptors involved in ATP-induced relaxation of porcine retinal arterioles in vitro.
abstract: OBJECTIVE
  Adenosine triphosphate (ATP) is involved in the tone regulation of retinal arterioles, and the effect may be direct, through ATP degradation or mediated by cyclo-oxygenase products. However, the relative contribution of these mechanisms and the extent to which the mechanisms are active in the retinal vascular wall or depend on the perivascular retinal tissue are unknown.
  
  
  METHODS
  Porcine retinal arterioles with perivascular retinal tissue were mounted in a wire myograph for isometric tone recordings. The relaxing effects of ATP and the non-degradable analogue ATP-x03B3;S were studied in the presence of antagonists to ATP, adenosine and prostaglandin E (EP) receptors. The experiments were repeated after removal of the perivascular retinal tissue.
  
  
  RESULTS
  ATP induced a significant concentration-dependent relaxation of retinal arterioles (p < 0.05) which was reduced after removal of perivascular retinal tissue. The effect was due to non-degraded ATP and a degradation product of ATP acting via adenosine receptors. Relaxation was reduced by ibuprofen and blocking of EP1 receptors.
  
  
  CONCLUSIONS
  ATP-induced relaxation of retinal arterioles is mediated by ATP, ATP degradation products and by stimulation of EP1 receptors, involving both the perivascular retina and the vascular wall. The findings emphasize the complexity of purinergic effects in the regulation of retinal vascular tone.
authors.affiliation: Department of Ophthalmology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Mette Ji
authors.initials: MJ
authors.lastname: Riis-Vestergaard
authors.forename: Toke
authors.initials: T
authors.lastname: Bek
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D001160:Arterioles / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009213:Myography; D058914:Purinergic Antagonists / Q000494:pharmacology; D058306:Receptors, Prostaglandin E, EP1 Subtype / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012161:Retinal Artery / Q000502:physiology*; D034421:Sus scrofa; D014664:Vasodilation / Q000187:drug effects
chemical_list: D058914:Purinergic Antagonists; D058306:Receptors, Prostaglandin E, EP1 Subtype; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate