Fig. 13.

Apoptosis induction through modulation of the NO concentration: the use of inhibitors of NO dioxygenase (NOD). The experiment was performed in exact analogy to the experiment described in Fig. 12, with the exception that the cellular NO concentration was modulated by either 1 μg/ml cyanidin or 1 μg/ml taxol instead of NOR-NOHA. Cyanidin and taxol inhibit NO dioxygenase, and thus raise the NO level of tumor cells [18,32]. The results confirm the validity of methods for the discrimination of primary and secondary singlet oxygen signatures. Both NO-dependent approaches did not indicate the action of primary singlet oxygen, but demonstrated the strong potential of cell-derived secondary singlet oxygen. Statistical analysis: Apoptosis induction in the control curves and the action of all inhibitors were highly significant (p < 0.001).