title: Bradykinin decreases outflow facility in perfused anterior segments and induces shape changes in passaged BTM cells in vitro.
abstract: OBJECTIVE
  To investigate the effects of bradykinin (BK) on the outflow facility (C) of human and bovine perfused anterior segments, the [Ca2+]i of cultured bovine trabecular meshwork (BTM) cells, and the area and major axis of BTM cells.
  
  
  METHODS
  Cellular studies were performed using first- through third-passage cultures of BTM cells. For [Ca2+]i and shape change assessment, BTM cells were loaded with fura-2 acetoxymethyl ester, and individual fluorescence images were analyzed after the different experimental manipulations. C studies were performed in vitro using human and bovine anterior segments perfused at constant pressure.
  
  
  RESULTS
  Bradykinin at 10(-6) M elicited a [Ca2+]i increase of 8 to 10 times the basal levels in 90% of the studied cells. From the responder cells, 60% elicited a 15%+/-1% reduction of the initial cell area, and 37% showed a 13%+/-2% reduction of their major axis. Bradykinin failed to induce any effect in the presence of the BK-B2 receptor antagonist HOE-140. Zero [Ca2+]o the depletion of intracellular stores with thapsigargin, or the presence of the calmodulin antagonist W13, decreased the BK response significantly (P < 0.001; P < 0.001; and P < 0.05). A second application of BK elicited a significantly lower (P < 0.001) response than the previous one. Perfusion with 10(-6) M BK decreased CD, calculated as the area under the curve, by 13%+/-4% (P < 0.05) in human anterior segments and 12%+/-4% (P < 0.05) in bovine anterior segments. The presence of 10(-6) M HOE-140, a BK-B2 receptor antagonist, completely blocked the decrease in C after perfusion with BK.
  
  
  CONCLUSIONS
  The C of human and bovine trabecular meshwork (perfused anterior segments) is decreased by BK, acting through BK-B2 receptors. Primary cultured BTM cells respond to BK stimulation by increasing their [Ca2+]i by mobilization of extracellular and intracellular Ca2+. Moreover, these cells are reduced in area and their major axis shortened after the [Ca2+]i peak elicited by BK through BK-B2 receptors. The [Ca2+]i mobilization and shape changes are calmodulin dependent. Taking into account the [Ca2+]i mobilization, the BTM shape changes, the decrease of C, and the temporal sequence of these parameters, a contraction of trabecular meshwork cells related to the functional role of trabecular meshwork is discussed.
authors.affiliation: Departament de Ciències Fisiològiques, Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Universitat de Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Llobet
authors.forename: A
authors.initials: A
authors.lastname: Gual
authors.forename: J
authors.initials: J
authors.lastname: Palés
authors.forename: R
authors.initials: R
authors.lastname: Barraquer
authors.forename: E
authors.initials: E
authors.lastname: Tobías
authors.forename: J M
authors.initials: JM
authors.lastname: Nicolás
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism*; D001920:Bradykinin / Q000031:analogs & derivatives / Q000494:pharmacology*; D065168:Bradykinin Receptor Antagonists; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002417:Cattle; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D010477:Perfusion; D013449:Sulfonamides / Q000494:pharmacology; D014129:Trabecular Meshwork / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
chemical_list: D065168:Bradykinin Receptor Antagonists; D002147:Calmodulin; D013449:Sulfonamides; C065679:icatibant; C033772:N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2