Autoradiograph showing the in vitro binding and degradation of ¹²⁵I-rmTPO by platelets. Mouse PRP was incubated with ¹²⁵I-rmTPO (TB) or ¹²⁵I-rmTPO + 10 μg rmTPO (NSB) at 37°C, or with ¹²⁵I-rmTPO alone at 4°C for 1 hour. ¹²⁵I-rmTPO was also incubated with buffer at 4°C or 37°C. Samples were then analyzed by SDS-PAGE. Approximate MW were determined from MW standards run on the same gel.