Figure 3. Effect of treatment of TK6 cells with 1,25-VD on the level of constitutive expression of γH2AX and ATM-S1981P. Exponentially growing TK6 cells were untreated (Ctrl) or treated with 10 nM 1,25-VD for 24 h. Expression of γH2AX and ATM-S1981P was detected in individual cells immunocytochemically, cellular fluorescence was measured by flow cytometry. The numbers above the arrows show the percent reduction in intensity of immunofluorescence of the mean values of cell populations in G1, S and G2M phases of the cell cycle in the 1,25-VD-treated cells with respect to the untreated cells (Ctrl) in the same phase of cell cycle.