title: Acute effects of prostaglandin D2 to induce airflow obstruction and airway microvascular leakage in guinea pigs: role of thromboxane A2 receptors.
abstract: BACKGROUND
  Although prostaglandin D2 (PGD2), a mast cell-derived inflammatory mediator, may trigger allergic airway inflammation, its potency and the mechanism by which it induces airway microvascular leakage, a component of airway inflammation, is not clear.
  
  
  OBJECTIVE
  We wanted to evaluate the relative potency of PGD2 to cause microvascular leakage as compared to airflow obstruction, because both responses were shown to occur simultaneously in allergic airway diseases such as asthma. The role of thromboxane A2 receptors (TP receptors) in inducing these airway responses was also examined.
  
  
  METHODS
  Anesthetized and mechanically ventilated guinea pigs were given i.v. Evans blue dye (EB dye) and, 1 min later, PGD2 (30, 100, 300 or 1,000 nmol/kg). For comparison, the effect of 150 nmol/kg histamine or 2 nmol/kg leukotriene D4 (LTD4) was also examined. Lung resistance (R(L)) was measured for 6 min (or 25 min for selected animals) and the lungs were removed to calculate the amount of extravasated EB dye into the airways as a marker of leakage. In some of the animals, specific TP receptor antagonists, S-1452 (10 microg/kg) or ONO-3708 (10 mg/kg), or a thromboxane A2 synthase inhibitor, OKY-046 (30 mg/kg), was pretreated before giving PGD2.
  
  
  RESULTS
  Injection of PGD2 produced an immediate and dose-dependent increase in RL (peaking within 1 min), which was significant at all doses studied. At 1,000 nmol/kg, PGD2 induced a later increase in R(L), starting at 3 min and reaching a second peak at 8 min. By contrast, only PGD2 at doses of 300 and 1,000 nmol/kg produced a significant increase in EB dye extravasation. The relative potency of 1,000 nmol/kg PGD2 to induce leakage as compared to airflow obstruction was comparable to histamine at most of airway levels, but less than LTD4. Both responses caused by PGD2 were completely abolished by S-1452 and ONO-3708, but not by OKY-046.
  
  
  CONCLUSIONS
  PGD2 may induce airway microvascular leakage by directly stimulating TP receptors without generating TXA2 in guinea pigs. Microvascular leakage may play a role in the development of allergic airway inflammation caused by PGD2.
authors.affiliation: Department of Pediatrics, Gunma University School of Medicine, Maebashi, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nishimura
authors.forename: K
authors.initials: K
authors.lastname: Tokuyama
authors.forename: Y
authors.initials: Y
authors.lastname: Inoue
authors.forename: H
authors.initials: H
authors.lastname: Arakawa
authors.forename: M
authors.initials: M
authors.lastname: Kato
authors.forename: H
authors.initials: H
authors.lastname: Mochizuki
authors.forename: A
authors.initials: A
authors.lastname: Morikawa
mesh_terms: D000402:Airway Obstruction / Q000139:chemically induced*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002196:Capillaries / Q000187:drug effects / Q000502:physiology; D002199:Capillary Permeability / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005070:Evans Blue / Q000378:metabolism; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D017998:Leukotriene D4 / Q000494:pharmacology; D008168:Lung / Q000378:metabolism / Q000473:pathology; D015230:Prostaglandin D2 / Q000494:pharmacology*; D017482:Receptors, Thromboxane / Q000378:metabolism*; D013930:Thromboxane-A Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013997:Time Factors
chemical_list: D017482:Receptors, Thromboxane; D005070:Evans Blue; D017998:Leukotriene D4; D006632:Histamine; D013930:Thromboxane-A Synthase; D015230:Prostaglandin D2