Western blot analysis demonstrates the presence of full-length TFPI in platelets. TFPI from plasma or from platelets lysed in 30 mM CHAPS buffer were precipitated with bovine factor Xa agarose and subjected to SDS-PAGE and Western blot analysis with either an antitotal TFPI antibody or an anti-TFPI antibody recognizing only the C-terminal 12 amino acids. Lanes 1 to 3 are stained for total TFPI; lanes 4 to 5 are stained for the C-terminal 12 amino acids. Lane 1 indicates platelet TFPI; lane 2, deglycosylated platelet TFPI; lane 3, plasma TFPI; lane 4, platelet TFPI; lane 5, deglycosylated platelet TFPI.