Effects of ultraviolet radiation on intercellular communication in V79 Chinese hamster fibroblasts

The effects of ultraviolet (UV) radiation on gap junctional intercellular communication (GJIC) in V79 Chinese hamster fibroblasts were studied by means of a dye transfer assay. Intercellular communication was shown to be altered by UVB (297/302 nm) and UVA (365 nm) radiation, the effect depending on the wavelength of exposure and time between irradiation and microinjection of the dye in the dye transfer assay. Exposure to 297/302 nm radiation induced a reduction in intercellular communication 6 min after exposure. Incubation of the cells post-irradiation reversed the inhibition of GJIC. From 2 to 24 h after exposure an increase in GJIC over the control cells was seen, with a maximum at 8 h post-irradiation. UVA (365 nm) radiation, on the other hand, induced an increase in the intercellular communication 6 min after irradiation. Incubation of the cells post-irradiation led to a decrease in the number of communicating cells, with a minimum seen 4 h after exposure. The reduction in communication observed after exposure to UVB and UVA was not correlated with similar modifications in the gap junction protein connexin43 as found when exposing the cells to the tumour promoter 12-O-tetradecanoyl-phorbol-13-acetate. For the higher fluences of UVA, a decrease in immunorecognizable connexin43 was seen, concomitant with a markedly increased background of higher mol. wt compounds. This may be due to UVA-induced crosslinking of connexin43. No correlation was found between changes in communication induced by UV radiation and levels of cyclic AMP.