CHI in mice induces time-dependent expansion of ICH. ICH induced by CHI was evaluated by MRI and by measuring extravasation of hemoglobin. (A) The hemorrhagic area was evaluated 24 hours post-CHI by T2*-weighted images in untreated WT mice (Control), mice given tPA-S⁴⁸¹A (1 mg/kg) either immediately after CHI (Treated) or 2 hours later (Treated 2 hrs). Images from 2 representative mice from each group (n = 5 each) are shown in the top and bottom panels. The hemorrhagic areas are delineated by circles. (B) Reduction in hemorrhage by tPA variant. WT mice were given saline (Cont) or tPA-S⁴⁸¹A (1 mg/kg) immediately after or 2 hours post-CHI, and the extravasation of hemoglobin into a lysate of whole brain was quantified by spectrophotometry³⁴  2, 8, or 24 hours later. The mean ± SD of 3 experiments performed in 5 to 7 mice is shown. (C) Comparative effect of inhibitors of plasminogen activation on hemorrhage 2 hours posttrauma. Immediately after CHI, WT mice were given saline (Cont), WT-tPA (5 mg/kg) or tPA-S⁴⁸¹A (1 mg/kg), WT-tPA (5 mg/kg) plus tPA-S⁴⁸¹A (5 mg/kg), tranexamic acid (TA; 150 mg/kg), aprotinin (Ap; 1 mg/kg), TA plus Ap, WT-tPA plus TA, WT-tPA plus Ap, or WT-tPA plus TA plus Ap, as indicated. Extravasation of hemoglobin into a lysate of whole brain was quantified by spectrophotometry³⁴  2 hours later. The mean ± SD of 3 experiments performed in 5 to 7 mice is shown. (D) Trauma induces tPA and uPA from brain parenchyma. The concentrations of tPA and uPA in the CSF of WT mice were measured by enzyme-linked immunosorbent assay before (Sham) or 2 hours after (Post) CHI. The mean ± SD of 3 experiments performed in 5 to 7 mice is shown. (E) Trauma induces fibrinolytic activity. The fibrinolytic activity of CSF was measured 2 hours post-CHI. Upper line: CSF (5 µL or 10 µL) obtained 2 hours after CHI from untreated mice was placed on top of plasma-derived clots as in Figure 2A. Lower line: CSF obtained 2 hours after CHI from mice treated with tPA-S⁴⁸¹A (1 mg/kg) immediately post-CHI. Data represent results from 1 of 3 independent experiments. (F) tPA variant inhibits fibrinolytic activity posttrauma. The fibrinolytic activity of CSF taken 2 hours after CHI from untreated mice or mice given tPA-S⁴⁸¹A (1 mg/kg) immediately posttrauma was quantified as in Figure 2B. The mean ± 2 SD of 3 experiments performed in 4 to 8 mice is shown. The statistical significance of experimental differences in this set of experiments and in those that follow was analyzed using 1-way analysis of variance with Newman-Keuls post hoc test.³³