Phototoxicity testing in vitro: evaluation of mammalian cell culture techniques

We have studied the effects of ultraviolet light on cells, and the phototoxic actions of a range of UV- or visible light-absorbing compounds in three separate in vitro tests (photolysis of red blood cells and phototoxicity to macrophages and to Chinese hamster CHV79 cells). Exposure to UV light for short periods was non-toxic to primary macrophages and red blood cells, but produced extensive killing of CHV79 cells. CHV79 cells can repair a considerable amount of UV-induced damage by unscheduled DNA synthesis but scheduled DNA synthesis is seriously disrupted. In vitro phototoxic compounds selectively damage discrete cellular components, such as the nucleus, plasma membrane or cytoplasmic organelles. Cellular damage can be shown to occur via two distinct photochemical pathways, either oxygen dependent or oxygen independent.