title: The removal of UV-induced pyrimidine dimers from DNA of rat skin cells in vitro and in vivo in relation to aging.
abstract: Young and old rats were compared with respect to the capacity of their skin fibroblasts and epidermal keratinocytes to remove low levels of ultraviolet light (UV) induced UV-endonuclease sensitive sites (pyrimidime dimers) from their DNA, in vitro and in vivo, respectively. In vitro, over a 24-h time period, fibroblasts from both young and old rats were found to remove about 20% of the pyrimidine dimers originally induced by 4.6 J/m2 of UV-C. In vivo, after 2.6 kJ/m2 of UV-B hardly any UV lesions were found to be present in fibroblasts, as demonstrated by immunohistochemistry using an anti-thymine dimer antibody. As reported earlier (Mullaart et al., J. Invest. Dermatol., 90 (1988) 346-349) cultured epidermal keratinocytes do not differ from cultured fibroblasts in UV repair kinetics, whereas in vivo they remove at least 50% of the pyrimidine dimers induced by 4 kJ/m2 of UV-B within 3 h. We now show that epidermal keratinocytes from old rats are not deficient in their in vivo repair characteristics upon this low UV-B dose. However, since a considerable fraction of the pyrimidine dimers appeared to be persistent in fibroblasts and keratinocytes, demonstrated by both enzymatic and immunochemical assays, the possibility is discussed that long-term exposure of skin cells to UV may lead to an accumulation of DNA damage with age.
authors.affiliation: TNO Institute for Experimental Gerontology, Rijswijk, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Mullaart
authors.forename: L
authors.initials: L
authors.lastname: Roza
authors.forename: P H
authors.initials: PH
authors.lastname: Lohman
authors.forename: J
authors.initials: J
authors.lastname: Vijg
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D000911:Antibodies, Monoclonal; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism / Q000528:radiation effects; D004260:DNA Repair; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000528:radiation effects; D007150:Immunohistochemistry; D011740:Pyrimidine Dimers / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012867:Skin / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D000911:Antibodies, Monoclonal; D011740:Pyrimidine Dimers; D004247:DNA