EXCISION REPAIR OF PYRIMIDINE DIMERS IN MARSUPIAL CELLS

Monodelphis domestica was further characterized as a model for photobiological studies by measuring the excision repair capabilities of this mammal's cells both in vivo and in vitro. Excision repair capability of the established marsupial cell line, Pt K2 ( Potorous tridactylus ), was also determined. In animals held in the dark, we observed that ?50% of the dimers were removed by 12 and 15 h after irradiation with 400 J m^?2 and 600 J m^?2, respectively, from an FS-40 sunlamp (280–400 nm). Cells from primary cultures of M. domestica excised ?50% of the dimers by 24 h after irradiating with 50 J m^?2 and 36 h after exposure to 100 J m^?2 with no loss of dimers observed 24 h following a fluence of 300 J m^?2. Pt K2 cells were observed to have removed -50% of the dimers at -12 h after 50 J m^?2 with only -10% of the dimers removed at 24 h following 300 J m^?2. The observed loss of pyrimidine dimers from epidermal DNA of UV-irradiated animals and from fibroblasts in culture, held in the dark, suggests that these marsupial cells are capable of DNA excision repair.