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SURVIVAL AND PYRIMIDINE DIMERS IN CULTURED FISH CELLS EXPOSED TO CONCURRENT SUN LAMP ULTRAVIOLET AND PHOTOREACTIVATING RADIATIONS
Author(s) -
SHIMA AKIHIRO,
SETLOW R. B.
Publication year - 1984
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1984.tb03403.x
Subject(s) - photolyase , irradiation , ultraviolet , pyrimidine dimer , dna , fluence , biology , pyrimidine , yield (engineering) , dna damage , microbiology and biotechnology , chemistry , dna repair , biochemistry , materials science , physics , optoelectronics , nuclear physics , metallurgy
— Cultured fishcells(RBCF–1 line) were irradiated with filtered sun lamp ultraviolet (SL‐UV; > 280 nm) together with or followed by illumination with daylight(DL) radiation (> 350 nm). The colony forming ability of the cells decreased with increasing fluence of SL‐UV. Concurrent exposure of cells to SL‐UV and DL, however, increased survival relative to exposure to SL‐UV alone. The photoreactivable fraction reached 0.52 at22–25 ‡ C. By using a constant fluence modification factor of 86, the shape of dose‐survival curve was found to be almost the same for 254 nm and SL‐UV. In parallel with photoreactivation of cell survival, changes in the numbers of pyrimidine dimers in permeabilized cell DNA and in extracted total DNA were determined by measurements of endonuclease‐sensitive sites (ESS). The yield of ESS in both DNA's increased almost linearly with increasing SL‐UV fluence, although the yield in extracted DNA was about double of that in permeabilized cell DNA. The yield of ESS per unit fluence by 254 nm was about 70‐fold greater than SL‐UV. The fraction of cells inactivated per ESS was almost the same for 254 UV and SL‐UV. In SL‐UV‐irradiated cells, the photoreactivable fractions in terms of ESS were ‡ 10% higher in extracted DNA than in the DNA of permeabilized cells and also were higher when DL was administered separately after SL‐UV‐irradiation. When irradiated cells were exposed to DL at 0 ‡ C, the photoreactivable fractions of both DNAs were appreciably less, indicating that the photoreactivation of ESS was enzymatic. These results support the suggestion that the mechanism for cell killing, mainly formation of pyrimidine dimers, by SL‐UV is the same as that by 254 UV.