Figure 4. (A) Dp44mT has no effect on the uptake of ¹²⁵I-HSA by human SK-N-MC cells as a function of concentration at 37°C.

SK-N-MC cells were incubated in media with ¹²⁵I-HSA (0.001-10 mg/mL) in the presence and absence of unlabeled Dp44mT (25 μM) for 2 h/37°C. Cells were washed in cold PBS, treated with Pronase (1 mg/mL) for 30 min/4°C and radioactivity of the resulting Pronase-sensitive (membrane-bound) fraction and the Pronase-insensitive (cellular fraction) was assessed. Results are expressed as mean ± S.E.M. from 3 experiments. (B) Effect of unlabeled (i) Dp44mT, (ii) Bp4eT, or (iii) PIH on the uptake of ¹²⁵I-HSA by SK-N-MC cells as a function of time at 37°C. SK-N-MC cells were incubated with ¹²⁵I-HSA (7.5 mg/mL) with or without unlabeled Dp44mT, Bp4eT, or PIH (25 μM) for 30 min/37°C. Subsequent steps were performed as above. (C) Effect of HSA (7.5 mg/mL) on (i) ¹⁴C-Dp44mT, (ii) ¹⁴C-Bp4eT or (iii) ¹⁴C-PIH (25 μM) uptake by SK-N-MC cells as a function of time at 37°C. Experiments were performed in parallel to those in Figure 6B, with the methodology being the same as that described in Figure 4A-C.