Failure of cold TPO to completely displace bound ¹²⁵I-rhTPO from platelets. Human PRP was incubated with ¹²⁵I-rhTPO for 30 minutes before the addition of a greater than 1,000-fold excess of cold TPO. Platelet-associated radioactivity (n = 2 per timepoint) was sampled before and after the addition of cold rhTPO.