Higher sensitivity in induction of apoptosis in fibroblast cell lines derived from LEC strain rats to ultraviolet B radiation

When lung fibroblast cell lines from LEC and WKAH rats were irradiated with ultraviolet B (UVB) and assayed for colony formation, LEC rat cells showed a higher sensitivity than did WKAH rat cells. The LEC rat cells were appro ximately 1.5-fold more sensitive to UVB radiation than were the WKAH rat ce lls in terms of D-37 values, which are the doses of UVB required to reduce cell survival to 37%. When the rat cells were irradiated with UVB in the pr esence of 0.5 M dimethyl sulfoxide (DMSO), which efficiently scavenges free radicals such as hydroxyl radicals, no significant difference was observed between the survival curves of either LEC or WKAH rat cells irradiated wit h UVB in the presence of 0.5 M DMSO and those irradiated with UVB in the ab sence of DMSO. Therefore, formation of free radicals may not be involved in cell death induced by UVB radiation. Flow cytometry showed that the percen tage of apoptotic cells in the LEC rat cell population increased with post- incubation time after UVB radiation. The proportion of apoptotic cells in t he UVB-irradiated LEC rat cell population increased as the dose of UVB was increased. In contrast, no significant proportion of apoptotic cells was ob served in the UVB-irradiated WKAH rat cell population. These results showed a higher sensitivity in induction of apoptosis by UVB radiation in LEC rat cells than in WKAH rat cells.