Blood from 4 individual subjects was drawn into P700, P800, and K2EDTA BD evacuated blood collection tubes. Immediately after collection, Linco™ DPP-IV inhibitor or aprotinin was added to designated K2EDTA tubes from each subject. The tubes were immediately centrifuged and the plasma pooled from each tube/inhibitor type collected. An equivalent volume of plasma from each tube/inhibitor type (P700, P800, K2EDTA, K2EDTA+Linco™ DPP-IV inhibitor, and K2EDTA+aprotinin) was spiked within 1 hour of collection with 800 pM of Active GLP-1 (7-36 amide). Each set of plasma pools prepared from each subject was maintained at 25±3°C. Plasma aliquots were taken at 0, 2, 4, 6, 12, 24, 48 and 72 hours and stored frozen below -60°C until assayed for Active GLP-1 by ELISA.