title: Surfactant barrier lining peritoneal mesothelium: lubricant and release agent.
abstract: OBJECTIVE
  Five studies are described to determine whether there is an outermost lining of surface-active phospholipid (SAPL) adsorbed to the peritoneum and to quantify its ability to act as a release (antistick) agent and boundary lubricant by standard tests.
  
  
  METHODS
  Using a hydrophobic probe (phosphin E), epifluorescence microscopy was used to demonstrate an outermost lining of oligolamellar SAPL by spectral analysis of the emitted light, a finding consistent with the appreciable hydrophobicity demonstrated on canine peritoneal mesothelium and its virtual elimination by incubation with bile salt. Good release and excellent lubricating capabilities of human peritoneal SAPL have been quantified as the release factor and coefficient of friction, respectively, by standard tests from the physical sciences.
  
  
  RESULTS
  A well-defined outermost layer was clearly visible on peritoneal mesothelium whose color spectrum was identical to that produced by pure phosphatidylcholine ultrasonicated into its oligolamellar state. Further evidence for a SAPL lining was demonstrated by a parietal contact angle of 43 degrees (47 degrees visceral) on this surface and its virtual elimination by incubation with dilute bile salt. Human SAPL from continuous ambulatory peritoneal dialysis (CAPD) effluent proved an effective release agent, reducing adhesion by 67%, and an excellent lubricant as quantified by a coefficient of friction of 0.091 under load (1.9 kg/cm2).
  
  
  CONCLUSIONS
  The good release and excellent lubricating properties of SAPL adsorbed to mesothelial surfaces are highly desirable in reducing wear and exfoliation of epithelial cells. In spanning epithelial cells, the same lining might also serve to render tight junctions tight and reduce macromolecular escape while compatible with many aspects of CAPD, including lipid permeability and conflicting results obtained from administering exogenous SAPL.
authors.affiliation: Paediatric Respiratory Research Centre, Mater Children's Hospital, South Brisbane, Queensland, Australia.
authors.forename: B A
authors.initials: BA
authors.lastname: Hills
authors.forename: J R
authors.initials: JR
authors.lastname: Burke
authors.forename: K
authors.initials: K
authors.lastname: Thomas
mesh_terms: D000818:Animals; D004285:Dogs; D004848:Epithelium / Q000502:physiology; D006801:Humans; D008153:Lubrication; D008856:Microscopy, Fluorescence; D010529:Peritoneal Cavity / Q000502:physiology*; D010531:Peritoneal Dialysis, Continuous Ambulatory; D012995:Solubility; D013501:Surface-Active Agents / Q000032:analysis*; D019108:Tight Junctions / Q000502:physiology; D014462:Ultrafiltration; D014867:Water / Q000737:chemistry
chemical_list: D013501:Surface-Active Agents; D014867:Water