title: Dual vasoactive effects of tolazoline on rabbit pulmonary arteries.
abstract: OBJECTIVE
  To determine the vasoactive effects of tolazoline on isolated rabbit pulmonary arteries.
  
  
  METHODS
  Prospective, in vitro, randomized, controlled trial.
  
  
  METHODS
  Experimental laboratory in a university-affiliated hospital.
  
  
  METHODS
  New Zealand White Rabbits.
  
  
  METHODS
  The pulmonary artery rings were obtained via thoracotomy. Their vasoactive responses were assessed in the presence and absence of intact endothelium and with or without precontraction by norepinephrine (NE, 3 x 10(-6) M) or potassium chloride (KCl, 3 x 10(-2) M). Using a tissue bath preparation, cumulative concentration response curves of tolazoline were obtained at different concentrations (10(-9) to 10(-4) M) after a period of stabilization.
  
  
  RESULTS
  Tolazoline caused vasoconstriction of isolated pulmonary arteries without any pretreatment. The magnitude of the constriction was dose related and reached 300 g/g wet tissue at a concentration of 10(-4) M. On KCl-precontracted pulmonary arteries, tolazoline caused significant dose-related vasoconstriction. On the NE-precontracted vessel rings, it elicited significant dose-dependent vasodilation up to 60% relaxation at 10(-5) M. All the above effects were endothelium independent.
  
  
  CONCLUSIONS
  Tolazoline has dual endothelium-independent vasoactive effects, causing vasoconstriction on isolated rabbit pulmonary arteries, either untreated or precontracted with KCl, and vasodilation on those precontracted with NE. Tolazoline may act as a competitive alpha-adrenoceptor blocking agent.
authors.affiliation: Department of Anesthesiology, Harbor-UCLA Medical Center, Torrance 90509-2910, USA.
authors.forename: T S
authors.initials: TS
authors.lastname: Lee
authors.forename: X
authors.initials: X
authors.lastname: Hou
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004730:Endothelium, Vascular / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000187:drug effects*; D011817:Rabbits; D011897:Random Allocation; D014043:Tolazoline / Q000008:administration & dosage / Q000494:pharmacology*; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000317:Adrenergic alpha-Antagonists; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D011189:Potassium Chloride; D014043:Tolazoline; D009638:Norepinephrine