title: Supernatant medium from UV-irradiated cells influences the cytotoxicity and mutagenicity of V79 cells.
abstract: It is known that UV light induces the secretion of some proteins into the extracellular medium. We have carried out experiments to study how the supernatant medium from UV-irradiated cells affects the cytotoxicity and mutagenicity of V79 cells exposed to different damaging agents. So we exposed exponentially growing cells to 20 J/m2 of UV light and then harvested the supernatant medium after 22 h. This supernatant medium was then used to treat a fresh batch of cells for 2 h. After the treatment with this supernatant medium the cells were subsequently exposed to UV light, gamma-rays, hydrogen peroxide or MNNG. We found that exposure to this medium had a protective effect on the survival levels for UV light, gamma-rays and hydrogen peroxide while MNNG-induced killing remained unaffected. With UV light and gamma-rays we found that mutation induction at all doses was increased. Cycloheximide could inhibit this protection and the increase in mutation frequencies was also suppressed. The results indicated a protective role for the UV-induced factor(s). They were probably involved directly or they triggered repair process(es) that were related to oxidative stress.
mesh_terms: D000818:Animals; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D002460:Cell Line; D006224:Cricetinae; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000494:pharmacology*; D003513:Cycloheximide / Q000494:pharmacology; D005720:Gamma Rays; D006861:Hydrogen Peroxide / Q000633:toxicity; D008769:Methylnitronitrosoguanidine / Q000633:toxicity; D009154:Mutation / Q000187:drug effects* / Q000528:radiation effects*; D018384:Oxidative Stress; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D017077:Culture Media, Conditioned; D011500:Protein Synthesis Inhibitors; D011506:Proteins; D008769:Methylnitronitrosoguanidine; D003513:Cycloheximide; D006861:Hydrogen Peroxide