Figure 4. Apoptotic death of pulp cells induced by NO. (A) Pulp cells were cultured in normal medium (Normal) or mineralization-promoting medium (MP) for 5 days in the absence or presence of 50 µM NOC-18. Cells were detached by collagenase digestion and stained with 10 µg/mL PI. Dead cells stained with PI were analyzed by flow cytometry. *The fraction of PI-positive cells was significantly higher in cells treated with NOC-18 compared with control cells (n = 4). (B) (Left panels) TUNEL staining was performed on the cells cultured for 5 days in MP medium in the absence (Control) or presence of 50 µM NOC-18 (NOC-18). (Right panels) The cells were counter-stained with 5 µg/mL Hoechst 33258.