title: Ketamine reduces nitric oxide biosynthesis in human umbilical vein endothelial cells by down-regulating endothelial nitric oxide synthase expression and intracellular calcium levels.
abstract: OBJECTIVE
  Ketamine, an intravenous anesthetic agent, can modulate vascular tone. Nitric oxide (NO), constitutively produced in endothelial cells, contributes to vasoregulation. In this study, we attempted to evaluate the effects of ketamine on NO biosynthesis in human umbilical vein endothelial cells and its possible mechanism.
  
  
  METHODS
  Controlled laboratory study
  
  
  METHODS
  Research laboratory in a universal hospital.
  
  
  METHODS
  Human umbilical vein endothelial cells prepared from human umbilical cord veins were exposed to 1, 10, 100, and 1000 microM ketamine for 1, 6, and 24 hrs.
  
  
  RESULTS
  Exposure to 1, 10, and 100 microM ketamine for 1, 6, and 24 hrs was not cytotoxic to human umbilical vein endothelial cells. However, ketamine at 1000 microM significantly caused cell apoptosis. A therapeutic concentration of ketamine (100 microM) time-dependently reduced the levels of nitrite in human umbilical vein endothelial cells. Immunoblot analysis revealed that ketamine time-dependently decreased endothelial NO synthase protein production in human umbilical vein endothelial cells. Results of an assay by reverse-transcription polymerase chain reaction showed that ketamine significantly inhibited levels of endothelial NO synthase messenger RNA. Ketamine time-dependently reduced bradykinin-enhanced intracellular calcium concentrations. Analysis by confocal microscopy further demonstrated the suppressive effects of ketamine on bradykinin-induced calcium mobilization.
  
  
  CONCLUSIONS
  A clinically relevant concentration of ketamine can reduce NO biosynthesis. The suppressive mechanisms occur not only by pretranslational inhibition of eNOS expression but also by a posttranslational decrease in endothelial NO synthase activity due to a reduction in intracellular calcium levels.
authors.affiliation: Graduate Institute of Medical Sciences, Department of Anesthesiology, Wan-Fang Hospital, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Ruei-Ming
authors.initials: RM
authors.lastname: Chen
authors.forename: Ta-Liang
authors.initials: TL
authors.lastname: Chen
authors.forename: Yi-Ling
authors.initials: YL
authors.lastname: Lin
authors.forename: Tyng-Guey
authors.initials: TG
authors.lastname: Chen
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Tai
mesh_terms: D000700:Analgesics / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D005260:Female; D006801:Humans; D007649:Ketamine / Q000494:pharmacology*; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D014471:Umbilical Veins
chemical_list: D000700:Analgesics; D009569:Nitric Oxide; D007649:Ketamine; D019001:Nitric Oxide Synthase