Thrombi formed from plasma depleted of FXIII or α₂AP show comparable lysis. (A) Plasma thrombi were prepared from pooled normal plasma (PNP; ○; n = 6) or plasma depleted of FXIII (●; n = 6), α₂AP (▴; n = 9), TAFI (▵; n = 2) and PAI-1 (□; n = 2) and lysed with 1 μg/mL tissue plasminogen activator (tPA). Lysis was monitored as release of fluorescence and expressed as mean ± SEM. FXIII and α₂AP depleted plasmas lysed significantly faster (P < .005) than PNP, TAFI, and PAI-1 depleted plasma, whereas FXIII and α₂AP depleted plasma lysed at comparable rates (P = .5). (B) Plasma thrombi were prepared from PNP (●, ○; n = 6) or α₂AP depleted plasma (▴, ▵;r n = 3) in the absence (closed symbols) and presence (open symbols) of a TG inhibitor. Thrombi were lysed as described in panel A. Lysis of α₂AP depleted plasma thrombi was significantly different from PNP (P < .005) but no difference in lysis was observed on incorporation of TG inhibitor into α₂AP depleted plasma before thrombus formation (P = .5). (C-E) Plasma thrombi were prepared from PNP or mixtures of PNP with FXIII (●) or α₂AP (▴) depleted plasma, resulting in different percentages of FXIII (0, 1.5, 6, 24, 48, 100%) or α₂AP (0, 20, 40, 60, 80, 100%) relative to their plasma concentration. Lysis was recorded as described in panel A and the mean lysis rate (FU/minutes) plotted against % PNP (n = 6; C). Alternatively, thrombi were solubilized in reducing sample buffer and subjected to SDS-PAGE followed by Western blotting for α₂AP (D; n = 6). The Western blot (D) was analyzed using Image J densitometry software and the peak area of total cross-linked α₂AP was plotted against the mean lysis rate for each sample of PNP and FXIII or α₂AP depleted plasma containing different percentages of plasma (E).