Zymogram shows that heparin administration induced MMP 9 up-regulation. (A) Zymographic analysis of protein extract from ischemic and nonischemic brains of WT and tPA KO mice at 48 hours after MCAO. (B-D) Densitometric analysis of zymographic gels. Pro–MMP 9 (B) and pro–MMP 2 (C) levels were significantly increased in the ischemic hemispheres in WT and tPA KO mice. The increase in pro–MMP 9 was exacerbated by heparin administration in WT mice but not in tPA KO mice (B). The active form of MMP 9 was detected only in the ischemic hemispheres and was significantly increased in heparin-treated WT mice (D). Values are means ± SD (n = 5). ^**P < .01; ##P < .01 compared with contralateral hemispheres.