title: Desflurane, compared to halothane, augments phenylephrine-induced contraction in isolated rat aorta smooth muscle.
abstract: OBJECTIVE
  The mechanism responsible for the mediation of hypertension in response to increased desflurane levels is unclear. This study compared the effect of desflurane and halothane on phenylephrine (PE)-induced contraction in rat aorta ring and the effect of desflurane in the presence and absence of nitric oxide (NO) synthase activity.
  
  
  METHODS
  Endothelium-free rat aorta rings were exposed serially to 10(-7) M, 10(-6) M and 10(-5) M PE alone and subsequently in the presence of 2 MAC desflurane and halothane. Secondly, endothelium-free preparations were exposed to 10(-6) M PE serially in the presence of 0, 1, 2 and 3 MAC desflurane and halothane. Thirdly, using an endothelium-intact preparation, the effect of desflurane on PE-induced contraction was examined, in the presence or absence of NG-nitro-L-arginine (L-NNA), an inhibitor of constitutive and inducible NO synthase.
  
  
  RESULTS
  Contraction amplitudes secondary to 10(-6) and 10(-5) M PE in endothelium-free preparations were increased by 74% and 36% respectively (P <0.05) in the presence of 2 MAC desflurane compared to controls. In endothelium-free preparations, contraction amplitudes secondary to 10(-6) M PE were increased in the presence of 1 and 2 MAC desflurane by 32% and 18% respectively (P <0.05) and reduced by 16% in the presence of 3 MAC halothane (P <0.05). In endothelium-intact preparations an expected absolute increase in contraction amplitude occurred in the presence of L-NNA but the desflurane effect was detectable both in the presence and absence of L-NNA.
  
  
  CONCLUSIONS
  Our results suggest that desflurane may have a local vasoconstrictive effect independent of endothelium and NO synthase activity. The mechanism remains to be determined.
authors.affiliation: Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut 06520-8051, USA. michael.griffin@yale.edu
authors.forename: M J
authors.initials: MJ
authors.lastname: Griffin
authors.forename: P M
authors.initials: PM
authors.lastname: Breen
authors.forename: J J
authors.initials: JJ
authors.lastname: O'Connor
authors.forename: V
authors.initials: V
authors.lastname: Hannon
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D002118:Calcium; D000077335:Desflurane; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000502:physiology; D006221:Halothane / Q000494:pharmacology*; D066298:In Vitro Techniques; D007530:Isoflurane / Q000031:analogs & derivatives / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D010656:Phenylephrine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D018685:Anesthetics, Inhalation; D010656:Phenylephrine; D000077335:Desflurane; D007530:Isoflurane; D002118:Calcium; D006221:Halothane