Figure 1.

Uptake of putrescine (a) and spermidine (b) by SW480 cells. Cells were seeded at 2.4 × 10⁴ cell/cm² on 24-well plates and grown for 48 h. Cells were pre-treated with DFMO (5 mM) for varying lengths of time (0–24 h). To measure uptake after exposure to DFMO, cells were incubated with radiolabelled polyamine at each DFMO exposure time for up to 4 h. The final concentration of radioactivity was 5.55 kBq/well (2.4 nM for putrescine or 5.6 nM for spermidine). Uptake was measured by liquid scintillation spectrometry. Values are mean ± SEM when n ≥ 3 or range when n < 3. Putrescine: (control and 24 h n = 6; 6 and 12 h n = 2; 3 h n = 1) with four replicates per experiment. Spermidine: (control and 24 h n = 3; 3 and 6 h n = 2; 12 and 18 h n = 1) with two replicates per experiment. For 24 h, P: ****<0.0001, compared to the respective control.