title: Aortic function in rats after decompression without ultrasonically detectable bubble formation.
abstract: BACKGROUND
  Several studies have demonstrated an adverse effect of bubbles on endothelial function. The degree of dysfunction appears to be related to the number of bubbles present. The aim of the study was to determine whether decompression without bubble formation visible by ultrasound had any effect on arterial endothelial function.
  
  
  METHODS
  We decompressed 21 Sprague-Dawley rats weighing 215-260 g from 700 kPa (approximately 6.9 ATA) in a dry hyperbaric chamber followed by a 1-h observation period and measured aortic endothelial-dependent relaxation to acetylcholine. Later, we determined the specific weight of the brain as a measure of edema formation and vascular bubbles in the arterial circulation.
  
  
  RESULTS
  No bubbles were seen in the pulmonary arteries of seven rats. We found a significant lower vasodilatory response to acetylcholine in the decompressed rats (44% +/- 14%) compared to the control rats (58% +/- 12%) as a sign of endothelial dysfunction. There was no significant difference between the two groups in the specific gravity of the brain.
  
  
  CONCLUSIONS
  We conclude that measurable arterial dysfunction in the aorta can occur even if no visible venous bubble formation is seen. There are no results in this study suggesting that these rats had damaged blood-brain barriers or brain edema.
authors.affiliation: Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway. kim-vidar.rasdal@ntnu.no
authors.forename: Kim-Vidar
authors.initials: KV
authors.lastname: Rasdal
authors.forename: Astrid
authors.initials: A
authors.lastname: Hjelde
authors.forename: Andreas
authors.initials: A
authors.lastname: Møllerløkken
authors.forename: Nina
authors.initials: N
authors.lastname: Lundset
authors.forename: Alp Ottar
authors.initials: AO
authors.lastname: Brubakk
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D001812:Blood-Brain Barrier / Q000502:physiology; D003665:Decompression Sickness / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D004618:Embolism, Air / Q000000981:diagnostic imaging*; D004730:Endothelium, Vascular / Q000503:physiopathology*; D005260:Female; D051381:Rats; D017207:Rats, Sprague-Dawley; D014463:Ultrasonography; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
chemical_list: D000109:Acetylcholine