title: A new histamine measurement system employing a confocal laser microscope and cultured human dermal microvascular endothelial cells.
abstract: BACKGROUND
  Histamine causes the endothelial cells of blood vessels to contract. H(1) receptor antagonists block histamine from binding to the H(1) receptor, suppressing edema. But it is unknown whether they bring about similar effects in microvascular endothelial cells in the human skin.
  
  
  OBJECTIVE
  We devised a series of experiments to measure changes in Ca(2+) concentration within human dermal microvascular endothelial cells stimulated with histamine using a confocal laser microscope. Within a distinct concentration range, the observed changes in Ca(2+) concentration were proportional to the amount of histamine administered, raising the possibility that trace amounts of histamine and the amount of histamine binding to H(1) receptors could be quantified.
  
  
  METHODS
  An experiment was conducted in which the H(1) receptor-antagonistic actions of eight antihistamines and anti-allergy drugs with antihistamine properties were quantitatively evaluated using a system for performing the above quantification. Each evaluated drug was preloaded within the range 10(-9)-10(-3) M, histamine 10(-6) M was added, and changes in the intracellular concentration of Ca(2+) were noted so as to evaluate the drugs' antagonism of the H(1) receptor.
  
  
  RESULTS
  Within the measurable range of the system, epinastine was the most effective of the drugs tested in inhibiting changes in Ca(2+) concentration in cells stimulated with histamine.
  
  
  CONCLUSIONS
  Our system can be used to quantitatively measure and compare the actions of H(1) receptor antagonists on dermal microvascular endothelial cells, providing valuable information for dermatologists.
mesh_terms: D018926:Anti-Allergic Agents / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism; D002478:Cells, Cultured; D003984:Dibenzazepines / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006632:Histamine / Q000378:metabolism* / Q000494:pharmacology; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D008833:Microcirculation; D018613:Microscopy, Confocal; D009994:Osmolar Concentration; D012867:Skin / Q000098:blood supply*
chemical_list: D018926:Anti-Allergic Agents; D003984:Dibenzazepines; D006634:Histamine H1 Antagonists; D007093:Imidazoles; D006632:Histamine; C053090:epinastine; D002118:Calcium