Figure 3. Fate of SBFn in Caco-2 Cells.

Polarized Caco-2 cells were incubated with 5 nmol/L ¹³¹I-labeled SBFn at 37°C for different times. Protein binding to the cell surface, determined by displacement of surface ¹³¹I-labeled SBFn by unlabeled SBFn (A), and protein degradation, determined as the soluble ¹³¹I radioactivity following 10% TCA precipitation (B), were measured as described in the Materials and Methods. C: The effects of cells and temperature on the release of ¹³¹I-ferritin degradation products were analyzed as described in the Methods section. The results are presented as the means and SD for three independent experiments done in triplicates.