Figure 8.

Degradation of Tf and cross-linked Tf bound to the wild-type TR. CEFs expressing wild-type TR were preincubated in serum-free medium for 30 min at 37°C and then incubated with ¹²⁵I-labeled Tf or ¹²⁵I-labeled cross-linked Tf for 10 min. at 37°C. The cells were then washed and reincubated at 37°C in DMEM containing 50 μg/ml unlabeled Tf and 0.1% BSA for various times. Acid-soluble radioactivity (○) or acid-insoluble ¹²⁵I-labeled Tf (▵) released into the medium, as well as surface bound Tf (□) and internalized (⋄) ¹²⁵I-labeled Tf was determined as described in Figure 5. A representative experiment of three is shown.