Figure 3

Comparison of uptake kinetics of rhTF and hTF in HeLa and Caco-2 cells. A. Uptake kinetics of rhTF and hTF in HeLa cells. One μg/ml of ¹²⁵I-labeled rhTF was added to confluent HeLa cells, and incubated at 37°C for 0.5, 1, 2, and 4 hr. In a comparison assay, 1 μg/ml of ¹²⁵I-hTF was added to confluent HeLa cells, and incubated at 37°C for 0.5 and 3 hr. Cells were then washed with cold PBS, solubilized with 1 N NaOH, and radioactivity in cell lysate was determined. B. Uptake kinetics of rhTF and hTF in Caco-2 cells. One μg/ml of ¹²⁵I-labeled hTF or rhTF was added to confluent Caco-2 cells and incubated at 37°C for 0.5, 1, 2, and 4 hr. Cells were then washed with cold PBS, solubilized with 1 N NaOH, and radioactivity in cell lysate was determined. The total cellular protein in the cell lysate was measured, and used to normalize the data to ng of hTF per mg cell protein (“ng/mg cell protein”). Data is represented as average with error bars indicating standard deviation, n = 3.