Proteolysis of ¹²⁵I-rhTPO by platelet lysates. Platelet lysates were prepared from washed PRP. Aliquots of the lysate were incubated with ¹²⁵I-rhTPO with or without protease inhibitors at 37°C for 5 hours. Degradation of ¹²⁵I-rhTPO was analyzed by SDS-PAGE and autoradiography. Approximate MW (determined from prestained MW markers) are listed on right axis (A). A densitometric analysis of the autoradiograph is presented in (B). Buf, buffer; SUP, supernatant; EDTA; Leu, leupeptin; Cal (−), Calpain inhibitor I; iodo, iodoacetic acid.