title: Impact of UVR-A on whole human lenses, supernatants of buffered human lens homogenates, and purified argpyrimidine and 3-OH-kynurenine.
abstract: OBJECTIVE
  Yellow chromophores and fluorescent compounds accumulate in the lens with age. Some of these compounds are photochemically active. The present study aimed to examine the photochemical effect of ultraviolet radiation-A (UVR-A) on the human lens.
  
  
  METHODS
  Intact human lenses and supernatants of buffered lens homogenates were exposed to UVR-A. The effect of UVR-A was evaluated by time-resolved and steady-state fluorescence spectroscopy, visual evaluation of colour and protein gel electrophoresis.
  
  
  RESULTS
  Intact lenses exposed to UVR-A showed no changes in time-resolved or steady-state fluorescence properties but the yellow coloration was visibly attenuated. The supernatants of buffered lens homogenates exposed to UVR-A demonstrated a reduction in time-resolved and steady-state fluorescent properties and protein cross-linking.
  
  
  CONCLUSIONS
  Exposure of the intact lens to UVR-A causes chromophore bleaching without affecting fluorescence, indicating that non-fluorescent chromophores have been destroyed. After homogenization, both chromophores and fluorophores from the lens suffer damage and proteins aggregate. This indicates that powerful mechanisms of protection against UVR-A found in the intact lens are disturbed by homogenization of the lens, suggesting that isolated lens proteins cannot be used as a model system for studying cataractogenesis. Hypothetically, the protective mechanism could be related to the rigidly packed three-dimensional structure of the lens proteins or to the abundance of antioxidative and free radical scavenging defence systems.
authors.affiliation: Department of Ophthalmology. Herlev Hospital. University of Copenhagen, Herlev, Denmark. line.kessel@dadlnet.dk
authors.forename: Line
authors.initials: L
authors.lastname: Kessel
authors.forename: Stanislav
authors.initials: S
authors.lastname: Kalinin
authors.forename: Vladislav
authors.initials: V
authors.lastname: Soroka
authors.forename: Michael
authors.initials: M
authors.lastname: Larsen
authors.forename: Lennart B-A
authors.initials: LB
authors.lastname: Johansson
mesh_terms: D000368:Aged; D000818:Animals; D002021:Buffers; D003459:Crystallins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007737:Kynurenine / Q000031:analogs & derivatives* / Q000528:radiation effects*; D007908:Lens, Crystalline / Q000378:metabolism / Q000528:radiation effects*; D008875:Middle Aged; D009952:Ornithine / Q000031:analogs & derivatives* / Q000528:radiation effects*; D010860:Pigments, Biological / Q000378:metabolism; D011743:Pyrimidines / Q000528:radiation effects*; D011829:Radiation Dosage; D011833:Radiation Injuries, Experimental / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D014466:Ultraviolet Rays
chemical_list: D002021:Buffers; D003459:Crystallins; D010860:Pigments, Biological; D011743:Pyrimidines; C107313:argpyrimidine; C005045:3-hydroxykynurenine; D007737:Kynurenine; D009952:Ornithine