Overall mean concentration of total radioactivity associated with platelets and spleens following IV administration of ¹²⁵I-rmTPO. Mice received a single IV bolus injection of ¹²⁵I-rmTPO or ¹²⁵I-rmTPO + 10 μg rmTPO and were killed 3 hours later. (A) Citrated blood was collected and the amount of radioactivity bound to platelets determined. The data were expressed as cpm bound. (B) Spleens were dissected and the amount of radioactivity associated with the spleens determined and reported as cpm/gram. *Indicates values are significantly different (P < .05).