Binding of ¹²⁵I-rhTPO by human PRP. PRP was incubated with ¹²⁵I-rhTPO with or without cold rhTPO for 30 minutes at 37°C. Platelet-associated radioactivity (n = 2 per data point) was used to determine affinity data from a four-parameter fit and receptor number via Scatchard analysis. Data from multible binding experiments using different PRP and ¹²⁵I-rhTPO preparations are presented in Table 1.