title: Acute effects of UVB radiation on the proliferation and differentiation of keratinocytes.
abstract: OBJECTIVE
  The effects of UVB radiation on the proliferation and differentiation of epidermal keratinocytes were investigated with respect to timing, dosage, and repeated exposures.
  
  
  METHODS
  Nine healthy volunteers were placed into three subgroups and exposed to UVB radiation on buttock skin using a Waldmann UV 800 unit fitted with Philips TL-20W/12 fluorescent lamps. Three volunteers were given 2 MED of UVB and biopsied at: pre-exposure, 24, 48 and 72 h after UVB exposure. For three volunteers, 1 MED, 2 MED, 3 MED of UVB were applied. After 48 h, biopsies were taken from non-irradiated and irradiated sites. Finally, three volunteers received 1 MED of UVB daily for 5 days, and the non-irradiated and irradiated sites were biopsied 48 h after the final exposure. The expression of proliferation and differentiation markers by keratinocytes were detected by immunohistochemical staining, and the results were analysed quantitatively by image analysis.
  
  
  RESULTS
  The expression of proliferation and differentiation markers was observed prominently 48 h after irradiation. Higher doses of UVB caused an increase in proliferation and differentiation marker expression. Repeated exposures potentiated the effect of UVB radiation.
  
  
  CONCLUSIONS
  UVB irradiation concomitantly promotes epidermal proliferation and differentiation. Responses were maximal 48 h after irradiation. This effect of UVB increases linearly according to dose and repetition.
authors.affiliation: Department of Dermatology, Seoul National University College of Medicine, Laboratory of Cutaneous Ageing Research, Clinical Research Institute, Seoul National University Hospital, Seoul, South Korea.
authors.forename: J H
authors.initials: JH
authors.lastname: Lee
authors.forename: H T
authors.initials: HT
authors.lastname: An
authors.forename: J H
authors.initials: JH
authors.lastname: Chung
authors.forename: K H
authors.initials: KH
authors.lastname: Kim
authors.forename: H C
authors.initials: HC
authors.lastname: Eun
authors.forename: K H
authors.initials: KH
authors.lastname: Cho
mesh_terms: D000328:Adult; D001706:Biopsy; D002081:Buttocks; D002455:Cell Division / Q000528:radiation effects; D006801:Humans; D007124:Immunoenzyme Techniques; D015603:Keratinocytes / Q000378:metabolism / Q000528:radiation effects*; D007633:Keratins / Q000378:metabolism; D019394:Ki-67 Antigen / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D012867:Skin / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D019394:Ki-67 Antigen; D008565:Membrane Proteins; D011498:Protein Precursors; C064554:loricrin; C032253:involucrin; D007633:Keratins