PHOTOREPAIR AND EXCISION-REPAIR REMOVAL OF UV-INDUCED PYRIMIDINE DIMERS AND (6-4)-PHOTOPRODUCTS IN THE TAIL PIN OF THE MEDAKA, ORYZIAS-LATIPES

Induction and repair of UV-B induced DNA damage in the tail fin of the Medaka, were examined immunohistochemically and by the enzyme-linked immunosorbent assay (ELISA). UV-induced DNA damage was detected only i n the outermost layer of epithelial cells and did not differ in fishes having different degree of melanization. Both pyrimidine dimers and ( 6-4) photoproducts in the fin cells were removed by excision repair in the dark, the excision of (6-4) photoproducts being about twice as ef ficient as that of pyrimidine dimers. The rate of excision repair of U V-induced lesions in fin tissue was three to four times that in cultur ed Medaka cells, OL32.. In the fin cells, reductions in the numbers of pyrimidine dimers and (6-4) photoproducts were seen after treatment w ith fluorescent light, whereas less reductions of pyrimidine dimers an d no reductions of (6-4) photoproducts were observed in OL32 cells.