Figure 1.

Directly applied NTP as well as NTP-treated medium conferred oxidative stress and reduced metabolic activity and cell proliferation. 6606PDA cells (a) and fibroblasts (b) were stained with CM-H₂DCF-DA and subsequently exposed to argon gas-treated (control, I) or NTP-treated (II) medium (60 s). The former had no effect on the redox status of the cells whereas the latter strongly oxidized 6606PDA tumor cells (a II) but not fibroblasts (b II). Representative images of two independent experiments are shown. Scale bars represent 50 µm. 6606PDA cells (c) or fibroblasts (d) were directly exposed to NTP (direct) or to NTP-treated medium (indirect) and their metabolic activity was assessed after 24 h. To examine cellular proliferation, 6606PDA cells (e) or fibroblasts (f) were exposed to NTP or NTP-treated medium and cellular BrdU incorporation was quantitatively measured 4 h later. Data are presented as mean + S.D. of three to five independent experiments.