Induction of apoptosis in cultured midbrain cells from embryonic mice

Midbrain cells from embryonic mice were cultured at a high cell density for 4 days to observe proliferation and differentiation. Results indicate that UVC radiation caused dose-dependent inhibition of their proliferation and differentiation. Inhibitory effects of UVC radiation (per unit dose) were greater on cell differentiation than on proliferation. The percentage of apoptotic cells in the groups irradiated with 15 J/m2 became significantly higher than the control level 2 h after irradiation. The percentage of apoptotic cells increased with time in a dose-associated fashion and reached a maximum at about 7.5 h after irradiation. Then it decreased with time and returned to the control level at about 30 h after irradiation. Metabolic inhibitors could postpone occurrence of intermediate apoptosis (>2 h, but <20 h) if they were added at suitable times after irradiation but failed to prevent a delayed apoptosis (>24 h). Results showed that UVC radiation induced intermediate apoptosis which could be postponed by metabolic inhibitors, and that UVC could also induce delayed apoptosis with the addition of metabolic inhibitors. The result that UVC radiation could induce intermediate apoptosis in the midbrain cells was different from previous data obtained using cells of an established cell line. The implications of the results for the understanding of the mechanism involved are discussed.