title: Investigations into the fate of inhaled salmon calcitonin at the respiratory epithelial barrier.
abstract: OBJECTIVE
  The fate of inhaled salmon calcitonin (sCT) at the respiratory epithelial barrier was studied with particular emphasis on enzymatic degradation by trypsin, chymotrypsin, and neutrophil elastase.
  
  
  METHODS
  Degradation of sCT was assessed by HPLC in cell homogenate, supernatant and intact monolayers of human respiratory epithelial cells (hBEpC, Calu-3, 16HBE14o-, A549) and Caco-2 as comparison at 37°C for 2 h. Breakdown of sCT by trypsin, chymotrypsin and neutrophil elastase was investigated. The presence of enzymes in cell supernatant and homogenate was studied by immunoblot and enzyme activity by model substrate assay. Transport studies across Calu-3 monolayers were performed.
  
  
  RESULTS
  sCT concentration remained unchanged over 2 h, when incubated in supernatant or with cell monolayers, independent of cell type studied. When cell homogenates were used, sCT concentrations were reduced to varying extents. sCT was degraded when incubated with enzymes alone. Western blot revealed abundance of all proteinases in cell homogenates and weaker expression in supernatants. Transport studies indicated net-absorptive sCT translocation; presence of bacitracin resulted in increased amount of sCT in receiver compartments.
  
  
  CONCLUSIONS
  Epithelial proteases play a role in the disposition of sCT after pulmonary delivery.
authors.affiliation: School of Pharmacy and Pharmaceutical Sciences, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Leonie
authors.initials: L
authors.lastname: Baginski
authors.forename: Frederic
authors.initials: F
authors.lastname: Tewes
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Buckley
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Healy
authors.forename: Udo
authors.initials: U
authors.lastname: Bakowsky
authors.forename: Carsten
authors.initials: C
authors.lastname: Ehrhardt
mesh_terms: D000280:Administration, Inhalation; D001692:Biological Transport; D015824:Blood-Air Barrier / Q000378:metabolism*; D018938:Caco-2 Cells; D002116:Calcitonin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D002918:Chymotrypsin / Q000378:metabolism; D006801:Humans; D019272:Leukocyte Elastase / Q000378:metabolism; D010024:Osteoporosis / Q000188:drug therapy; D020545:Respiratory Mucosa / Q000378:metabolism*; D014357:Trypsin / Q000378:metabolism
chemical_list: C028815:salmon calcitonin; D002116:Calcitonin; D002918:Chymotrypsin; D019272:Leukocyte Elastase; D014357:Trypsin