Increase in circulating APC levels during infusion of PCA or APC. Circulating APC levels were determined using an enzyme immunocapture assay. Both treatments resulted in increased APC levels, with the highest values observed in the high-dose PCA (8.3 μg/kg) and APC (222 μg/kg) treatment groups. APC levels reached 5-fold over baseline by the end of low-dose PCA (2.1 μg/kg) infusion, and 9-fold in the lower-dose APC (28 μg/kg) treatment groups.