title: The concentration-dependent contractile effect of methylene blue in the human internal mammary artery: a quantitative approach to its use in the vasoplegic syndrome.
abstract: OBJECTIVE
  To quantitate the contractile effect of methylene blue on isolated human internal mammary artery (IMA) as used in the vasoplegic syndrome.
  
  
  METHODS
  An in vitro experimental study.
  
  
  METHODS
  Cardiovascular Pharmacology Laboratory, Department of Medical Pharmacology.
  
  
  METHODS
  IMA segments were used from 24 patients undergoing coronary artery bypass surgery.
  
  
  METHODS
  The responses to methylene blue, norepinephrine, and acetylcholine were recorded isometrically by a force-displacement transducer in an isolated organ bath.
  
  
  RESULTS
  Methylene blue (10 nmol/L-100 micromol/L) produced concentration-dependent contraction in the arteries. The maximal contraction to methylene blue was 44.2% +/- 3.8% of KCl (68 mmol/L) maximum contraction; the pEC(50) (-log(10) of 50% effective concentration) value was 5.5 +/- 0.1. Methylene blue caused an insignificant leftward shift of the concentration-response curve of norepinephrine. Acetylcholine-induced relaxation in submaximal contracted rings with phenylephrine recovered nearly 6 hours after the methylene blue challenge.
  
  
  CONCLUSIONS
  Methylene blue caused concentration-dependent contraction in human IMAs. Furthermore, the inhibition of ACh-induced relaxation for 6 hours after the methylene blue challenge points out an additional mechanism (ie, receptor occupation). The concentration-dependent contractile effect of methylene blue justifies its use in the vasoplegic syndrome. The findings also suggest that the time course of contraction is longer than the exposure to methylene blue.
authors.affiliation: Department of Pharmacology, Gulhane School of Medicine, Ankara, Turkey.
authors.forename: Hasan B
authors.initials: HB
authors.lastname: Ulusoy
authors.forename: Husamettin
authors.initials: H
authors.lastname: Gul
authors.forename: Melik
authors.initials: M
authors.lastname: Seyrek
authors.forename: Oguzhan
authors.initials: O
authors.lastname: Yildiz
authors.forename: Cunay
authors.initials: C
authors.lastname: Ulku
authors.forename: Vedat
authors.initials: V
authors.lastname: Yildirim
authors.forename: Erkan
authors.initials: E
authors.lastname: Kuralay
authors.forename: Turgay
authors.initials: T
authors.lastname: Celik
authors.forename: Omer
authors.initials: O
authors.lastname: Yanarates
mesh_terms: D000328:Adult; D000368:Aged; D004305:Dose-Response Relationship, Drug; D006801:Humans; D066298:In Vitro Techniques; D008323:Mammary Arteries / Q000187:drug effects* / Q000502:physiology; D008751:Methylene Blue / Q000008:administration & dosage*; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D013577:Syndrome; D014661:Vasoconstriction / Q000187:drug effects* / Q000502:physiology
chemical_list: D008751:Methylene Blue