Susceptibility of iodinated plasma FBG to thrombin and plasmin action in A549 cell medium in the presence or absence of serum. ¹²⁵I-labeled FBG was added to serum-free medium and treated with plasmin (A) or thrombin (B) or to A549 conditioned 10% serum-containing medium (C). (A) represents an autoradiograph of a nonreduced, 8% polyacrylamide gel. (B) and (C) represent 7% polyacrylamide gels of reduced fibrin(ogen) polypeptide chains. (A) Lane 1, M_r denoted by arrowheads are, from top to bottom, 200, 97, 68, and 46 kD; lane 2, plasmin-cleaved ¹²⁵I-FBG fragments D and E (arrows, top to bottom); lane 3, ¹²⁵I-FBG plasmin-treated in the presence of 200 U/mL aprotinin; lane 4, ¹²⁵I-FBG starting material. (B) Lane 1, untreated ¹²⁵I-FBG Aα, Bβ, and γ chains; lane 2, thrombin-cleaved fibrin α, β, and γ chains. (C) Lane 1, ¹²⁵I-FBG in serum-free medium; lane 2, ¹²⁵I-FBG + hirudin and aprotinin; lane 3, ¹²⁵I-FBG + hirudin; lane 4, ¹²⁵I-FBG + aprotinin.