title: Oxygen-dependent regulation of membrane potential and vascular tone of human umbilical vein.
abstract: OBJECTIVE
  We question the hypothesis that vascular tone of human umbilical vein is insensitive to oxygen pressure and minimal already at resting conditions.
  
  
  METHODS
  Isometric tension and intracellular membrane potential of native (n = 7) and endothelium-denuded (n = 7) human umbilical vein strips were recorded simultaneously at oxygen pressure values of 5 to 104 mm Hg.
  
  
  RESULTS
  Increasing oxygen pressure from 5 to 104 mm Hg led to graded membrane depolarization from -58.2 +/- 1.3 mV (SEM) to -54.0 +/- 0.7 mV (P <.009) and increased isometric tension from 0.576 +/- 0.016 g to 0.790 +/- 0.032 g (P <.0001). The steepest increase in tension (Delta = 0.063 g) occurred within the physiologic intrauterine oxygen tension range (27-35 mm Hg). Isometric tension at hypoxia (partial oxygen pressure, 5 mm Hg) corresponded to 88% of resting tension. Tension and membrane potential were related linearly (r(2) = 0.99). Disruption of the endothelium reversed the effects of oxygen pressure.
  
  
  CONCLUSIONS
  Human umbilical vein vascular tone was regulated by oxygen tension and showed a hypoxic vasodilator reserve. Oxygen-dependent effects were related to the membrane potential and required the endothelium.
authors.affiliation: Department of pediatrics, Universitatsklinikum Benjamin Franklin, Berlin, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Mildenberger
authors.forename: G
authors.initials: G
authors.lastname: Siegel
authors.forename: H T
authors.initials: HT
authors.lastname: Versmold
mesh_terms: D004730:Endothelium, Vascular / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D010100:Oxygen / Q000008:administration & dosage / Q000494:pharmacology*; D010313:Partial Pressure; D014471:Umbilical Veins / Q000187:drug effects / Q000502:physiology*
chemical_list: D010100:Oxygen