Heparin administration induced tPA activity and mRNA expression. (A-B) Time course of tPA activity after MCAO in ischemic and nonischemic hemispheres in WT mice. Compared with the untreated mice, heparin-treated mice had significantly higher tPA activity in the ischemic hemisphere at 6 and 12 hours (A). No significant difference in tPA activity in the nonischemic hemisphere was noted between heparin-treated and untreated mice (B). Values are means ± SD (n = 4 or 5). ^*P < .05; ^**P < .01. (C) In the ischemic border zone, tPA activity was further increased by heparin administration at 6 hours. Values are means ± SD (n = 5). (D) Northern blot analyses of tPA mRNA expression 6 and 12 hours after MCAO in ipsilateral and contralateral cerebral hemispheres of ischemia in WT mice, which was normalized by the expression of β-actin (E). Compared with the untreated mice, heparin-treated mice had significantly higher tPA mRNA levels in ischemic hemispheres at 6 and 12 hours. Ethidium bromide staining of the 28S ribosomal RNA revealed equal RNA loading in all lanes. Values are means ± SD (n = 4). ^*P < .05; #P < .05 compared with contralateral hemispheres.