Effect of IR injury on renal TF mRNA expression and functional activity. (A,C,D) TF mRNA was measured in extracts of kidney tissue from WT (n = 12), WT hirudin-treated (n = 7-9/time point), and PAR-1^−/− mice (n = 12) at varying times (2, 5, and 24 hours) following renal IR injury or sham surgery (n = 6). (All values are expressed relative to 18S ribosomal RNA, and data are shown as mean ± SEM.) TF mRNA was increased at 2 hours after reperfusion and remained elevated for 24 hours (at all points **P < .001). TF mRNA was not increased in any sham-operated WT or PAR-1^−/− animals (WT only shown). (B,D,F) TF functional activity (measured from extracts of kidney tissue using a 1-stage prothrombin assay) was increased in WT mice (n = 16) or PAR-1^−/− mice (n = 16) at varying times (2, 5, and 24 hours) following renal IR injury compared with sham surgery (n = 6) (at 2 and 24 hours, **P < .005; at 5 hours, ***P < .05). Renal TF activity was very low from low-TF mice at all time points, and WT hirudin-treated mice had relatively reduced levels of TF activity (n = 7-9/group). IR injury resulted in no significant difference in TF expression between WT and PAR-1^−/− mice. (All values are expressed in relative units compared with a standard curve of rabbit thromboplastin in which a 1 in 10 dilution of standard was designated 100 units.)