Supernatant medium from UV-irradiated cells influences the cytotoxicity and mutagenicity of V79 cells.

摘要

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.