Effects of tPA on PKal activity in mouse plasma. (A) Concentration-response curves of tPA in WT and Klkb1^−/− mice plasma. Purified human tPA (0-360 nM) was incubated in mouse plasma in vitro for 10 minutes at room temperature. Kallikrein-like activity was measured as fluorescence at 410 nm because of hydrolysis of D-Pro-Phe-Arg-7-Amino-4-Trifluoromethylcoumarin. Data are expressed as ∆ fluorescence intensity per minute and represent mean ± SEM of 3 independent experiments. ***P < .001 vs baseline. (B) Concentration-response curves of tPA in WT and FXII^−/− mice plasma. Purified human tPA (0-360 nM) was incubated in mouse plasma in vitro for 10 minutes at room temperature. Data are expressed as ∆ fluorescence intensity per minute and represent mean + SEM of 3 independent experiments. ***P < .001 vs baseline. (C) Bar graph displays the time course of HK in WT mouse plasma incubated with tPA (360 nM). Representative western blot image is shown on top of the bar graph. Data are presented as mean ± SEM, n = 4. *P < .05 vs baseline. (D) Bar graph displays the time course of HK in Klkb1^−/− mouse plasma incubated with tPA (360 nM). Representative western blot image is shown on top of the bar graph. Data are presented as mean ± SEM, n = 4. (E) Bar graph displays the time course of HK in FXII^−/− mouse plasma incubated with tPA (360 nM). Representative western blot image is shown on top of the bar graph. Data are presented as mean ± SEM, n = 4. (F) Time-response of PPK activation in mouse plasma after tPA injection. Mice were treated intravenously with tPA (10 mg/kg) and blood collected at 15, 30, 45, and 60 minutes after injection. Data are expressed as ∆ fluorescence intensity per minute and represent mean ± SEM of 4 independent experiments. *P < .05 vs baseline. (G) Bar graph displays the time course of PKal generation after tPA injection. Representative western blot image is shown on top of the bar graph. Data are presented as mean ± SEM, n = 4. *P < .05 vs baseline.