title: Comparative study of ROS degradation by IPE and RPE cells in vitro.
abstract: BACKGROUND
  The aim of this study was to compare the degradation of rod outer segments (ROS) in porcine iris pigment epithelial cells (IPE) and retinal pigment epithelial (RPE) cells by measuring the increase of lipofuscin-like fluorescence.
  
  
  METHODS
  We measured the development of autofluorescence of lipofuscin-like material in living cells over a period of 4 weeks using an image-analyzing system comprising a light microscope, a filter set with an appropriate wavelength for the detection of lipofuscin-like autofluorescence and a silicon-intensified target camera connected to a computer. The lipofuscin-like fluorescence was quantified as the mean gray value of pixels over a defined area in the cell. In addition, ultrastructural examination of the cells was performed using transmission electron microscopy.
  
  
  RESULTS
  We found that while both cell types had increased autofluorescence over time, the increase of lipofuscin-like fluorescence was significantly higher in IPE cells than in RPE cells. The ultrastructure of both cell types was similar and no accumulation of lipofuscin-like granules was observed.
  
  
  CONCLUSIONS
  These findings suggest that although IPE cells are able to phagocytize ROS, their ability to degrade them may be lower than in RPE cells. The increase of lipofuscin-like fluorescence is not due to the accumulation of lipofuscin-like granules.
authors.affiliation: Department of Vitreoretinal Surgery, University Eye Clinic, Joseph Stelzmann Strasse 9, D-50931 Cologne, Germany,
authors.forename: T S
authors.initials: TS
authors.lastname: Dintelmann
authors.forename: K
authors.initials: K
authors.lastname: Heimann
authors.forename: P
authors.initials: P
authors.lastname: Kayatz
authors.forename: U
authors.initials: U
authors.lastname: Schraermeyer
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005453:Fluorescence; D007498:Iris / Q000166:cytology / Q000502:physiology*; D008062:Lipofuscin / Q000737:chemistry / Q000378:metabolism; D010587:Phagocytosis / Q000502:physiology*; D010857:Pigment Epithelium of Eye / Q000502:physiology* / Q000648:ultrastructure; D012160:Retina / Q000166:cytology / Q000502:physiology*; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D013552:Swine
chemical_list: D008062:Lipofuscin