title: Separate basolateral and apical phosphatidylcholine secretion routes in intestinally differentiated tumor cells.
abstract: OBJECTIVE
  To investigate whether the secretion of phosphatidylcholine (PC) in intestinal mucus occurs by apical secretion or via basolateral excretion and to determine its subsequent passage across the tight junctions to the apical mucus.
  
  
  METHODS
  We addressed this question using the polarized intestinally differentiated tumor cell line CaCo-2 grown on filters to confluence in Transwell culture chambers. The released PC and sphingomyelin (Sph) from apical and basolateral media were analyzed by mass spectrometry.
  
  
  RESULTS
  The secreted PC species were identical in both compartments indicating the same intracellular origin of PC. However, PC secretion into the basolateral compartment was more effective, and the PC:Sph ratio in the basolateral compartment was significantly higher than that in the apical compartment (8.18 +/- 1.84 vs 4.31 +/- 1.22, P = 0.01). Both pathways were temperature sensitive and were unaltered in the presence of cyclosporine.
  
  
  CONCLUSIONS
  The data demonstrate the PC secretion capacity of CaCo-2 cells and indicate two separated apical and basolateral release mechanisms.
authors.affiliation: Department of Gastroenterology, University Hospital Heidelberg, 69120 Heidelberg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gotthardt
authors.forename: Annika
authors.initials: A
authors.lastname: Braun
authors.forename: Anke
authors.initials: A
authors.lastname: Tietje
authors.forename: Karl Heinz
authors.initials: KH
authors.lastname: Weiss
authors.forename: Robert
authors.initials: R
authors.lastname: Ehehalt
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Stremmel
mesh_terms: D000818:Animals; D018938:Caco-2 Cells / Q000166:cytology / Q000378:metabolism*; D002454:Cell Differentiation; D016764:Cell Polarity; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D019108:Tight Junctions / Q000378:metabolism
chemical_list: D010713:Phosphatidylcholines