title: Non-invasive measurement of endothelial function: effect on brachial artery dilatation of graded endothelial dependent and independent stimuli.
abstract: OBJECTIVE
  To examine the relation between endothelial dependent and endothelial independent stimuli of varying intensity and measures of vascular function in the brachial artery of young healthy adults, to determine whether these responses are consistent and can be used to assess endothelial function.
  
  
  METHODS
  High resolution ultrasound was used to measure brachial artery diameter at rest, after reactive hyperaemia induced by forearm cuff occlusion, and after sublingual isosorbide dinitrate (ISDN). Each subject was assigned to a random order of six cuff occlusion times (30 seconds, 1.5, 2.5, 3.5, 4.5, and 8 minutes) and six doses of ISDN (10, 20, 50, 100, 200, and 400 micrograms).
  
  
  METHODS
  Three males and three females mean age 31 years (range 25 to 43) with no known risk factors for cardiovascular disease.
  
  
  METHODS
  Flow mediated, endothelial dependent dilatation was compared to duration of cuff occlusion, peak reactive hyperaemia, and duration of increased flow. Nitrate induced, endothelial independent dilatation was compared to dose of ISDN and change in flow.
  
  
  RESULTS
  Vessel dilatation and duration of peak flow change increased with longer duration of cuff occlusion. After 4.5 minutes of occlusion, flow mediated dilatation was mean (SD) 96 (6)% of maximal response and did not increase significantly with longer occlusion times. No significant dilatation occurred after 10 or 20 micrograms of ISDN in any subject. With increasing doses up to 200 micrograms there was an increase in dilatation. Endothelial independent dilatation did not increase significantly with doses of ISDN above 200 micrograms.
  
  
  CONCLUSIONS
  Measures of arterial function vary with duration of blood flow occlusion and ISDN dose. Maximum arterial response was reached in all subjects after 4.5 minutes of blood flow occlusion or 200 micrograms of ISDN. Therefore, these variables produce consistent reproducible measures of endothelial function.
authors.affiliation: Vascular Physiology Unit, Great Ormond Street Hospital, London, United Kingdom.
authors.forename: P
authors.initials: P
authors.lastname: Leeson
authors.forename: S
authors.initials: S
authors.lastname: Thorne
authors.forename: A
authors.initials: A
authors.lastname: Donald
authors.forename: M
authors.initials: M
authors.lastname: Mullen
authors.forename: P
authors.initials: P
authors.lastname: Clarkson
authors.forename: J
authors.initials: J
authors.lastname: Deanfield
mesh_terms: D000328:Adult; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000502:physiology* / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D007548:Isosorbide Dinitrate / Q000494:pharmacology*; D008297:Male; D012039:Regional Blood Flow; D014463:Ultrasonography; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D014665:Vasodilator Agents; D007548:Isosorbide Dinitrate