title: Loss of endothelium mediated vascular relaxation as a response to various clamping pressure. Part I. A pharmacological study.
abstract: BACKGROUND
  The contraction/relaxation response of thoracic aortal rings clamped with two clamping pressures to KCl, noradrenaline and carbachol was studied.
  
  
  METHODS
  Clamp A had the tip pressure PA = 0.60 N/mm2 and clamp B PB = 5.16 N/mm2. In fifteen Wistar albino rats, weighing 328 +/- 19 g (mean +/- SD) the thoracic aorta was occluded for 15 minutes and then three vascular rings (2 mm wide) were excised. The proximal unclamped ring served as a control. From distal rings the diameter of the aorta was calculated from their circumference 1.61 +/- 0.01 mm (n = 15, dmin = 1.51 mm, dmax = 1.70 mm). The rings were challenged with cumulative additions of KCl (10-80 mmol/l) to measure the contraction. Then cumulative relaxation to carbachol (0.01-100 mumol/l) as a response to noradrenaline precontraction (0.1 mumol/l) was determined.
  
  
  RESULTS
  A significant loss (p < 0.05) of vascular relaxation in all clamped rings (clamped with PA and PB clamping pressures) was seen. No significant differences (p > 0.05) were observed for contraction between clamped and control rings clamped with clamp A, however the rings clamped with clamp B showed a significant reduction in contraction (p < 0.05). No significant differences were seen from control rings between groups A and B (p > 0.05), or from clamped rings between groups A and B (p > 0.05) for both the contraction and relaxation part of experiments.
  
  
  CONCLUSIONS
  Endothelial vascular layers are much more susceptible to pressure injuries than was previously believed.
authors.affiliation: Department of Cardiovascular Surgery, Medical Centre Ljubljana, Slovenia.
authors.forename: B
authors.initials: B
authors.lastname: Gersak
authors.forename: R
authors.initials: R
authors.lastname: Trobec
authors.forename: I
authors.initials: I
authors.lastname: Krisch
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D003250:Constriction; D004730:Endothelium, Vascular / Q000187:drug effects / Q000293:injuries / Q000502:physiology*; D066298:In Vitro Techniques; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000502:physiology*; D011312:Pressure; D051381:Rats; D017208:Rats, Wistar; D013525:Surgical Instruments; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology