Kinetics of FpA and FpB release. Defibrinated control (●) and STAT5-deficient (○) plasma were supplemented with 1.0 mg/mL human fibrinogen. Reactions were initiated with thrombin and quenched at the indicated time points. FpA and FpB were quantified by HPLC analysis and normalized to the calculated FpA max values for each sample. FpA: STAT5-deficient (□) and control (■) mice had comparable release of FpA over time (n = 4; P = .6731; P > .05 at all time points; 2-way ANOVA with matching and Bonferroni post test). The rate constant, k1, was derived by fitting FpA curves to a first-order reaction (black lines); the rate of FpA release was similar between genotypes (n = 4; P = .5705; F test). FpB: In contrast, STAT5-deficient mice (○) demonstrated greater release of FpB over time compared with controls (●; n = 4; P = .0119; P < .05 at 0.5-, 2-, and 5-minute time points; 2-way ANOVA with matching and Bonferroni post test). Data points were plotted with a simple connecting line (gray lines).