title: Media: lumen ratio in human small resistance arteries is related to forearm minimal vascular resistance.
abstract: BACKGROUND
  For the evaluation in humans of structural alterations in resistance arteries, most studies have used an indirect index, the measurement of minimal vascular resistance (mean blood pressure divided by maximal postischaemic blood flow) in suitable vascular beds. A sensitive and specific micromyographic technique was recently made available for the study of human small resistance arteries. Whether a correlation really exists between results obtained with the two techniques has not yet been investigated.
  
  
  OBJECTIVE
  To evaluate both forearm minimal vascular resistance and media:lumen ratio of omental or subcutaneous small arteries in normotensive subjects and hypertensive patients.
  
  
  METHODS
  Thirty-four individuals were included in the study (age range 35-74 years; 24 hypertensive, 10 normotensive). Twenty-five had elective abdominal surgery and nine hypertensive patients had a gluteal biopsy. Omental and subcutaneous small arteries were dissected and mounted on a wire micromyograph (Mulvany's technique), and media:lumen ratio and media thickness were measured. The dose-response curve to noradrenaline was constructed at cumulative concentrations from 3 x 10(-9) to 3 x 10(-5) mol/l. Venous occlusion plethysmography was used to measure blood flow in the forearm, and minimal vascular resistance was calculated from mean blood pressure and postischaemic maximal blood flow (13 min ischaemia plus exercise).
  
  
  RESULTS
  A statistically significant correlation was found between media:lumen ratio and minimal vascular resistance (r = 0.74, P < 0.001) as well as between media:lumen ratio and systolic (r = 0.44, P < 0.01) and diastolic (r = 0.38, P < 0.05) blood pressures. Similar correlations were observed between media thickness and systolic and diastolic blood pressures. Small arteries from hypertensive patients had a significantly increased reactivity to noradrenaline (by analysis of variance) compared with those from normotensive subjects, in terms of wall tension but not of active media stress.
  
  
  CONCLUSIONS
  The present study demonstrated that the media:lumen ratio of small resistance vessels is significantly related to forearm minimal vascular resistance, suggesting that direct and indirect evaluations of vascular morphology will give similar results.
authors.affiliation: Semeiotica and Metodologia Medica, University of Brescia, Italy.
authors.forename: E A
authors.initials: EA
authors.lastname: Rosei
authors.forename: D
authors.initials: D
authors.lastname: Rizzoni
authors.forename: M
authors.initials: M
authors.lastname: Castellano
authors.forename: E
authors.initials: E
authors.lastname: Porteri
authors.forename: R
authors.initials: R
authors.lastname: Zulli
authors.forename: M L
authors.initials: ML
authors.lastname: Muiesan
authors.forename: G
authors.initials: G
authors.lastname: Bettoni
authors.forename: M
authors.initials: M
authors.lastname: Salvetti
authors.forename: P
authors.initials: P
authors.lastname: Muiesan
authors.forename: S M
authors.initials: SM
authors.lastname: Giulini
mesh_terms: D000328:Adult; D000368:Aged; D001158:Arteries / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D005542:Forearm / Q000098:blood supply; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D017540:Tunica Media / Q000473:pathology*; D014655:Vascular Resistance