The Effect of Trypsin and Storage on Aggregation and Release of Human Gel-Filtered Platelets

Abstract

Trypsin was studied as an aggregating and release-inducing agent with gel-filtered platelets (GFP) and was compared with ADP, epinephrine and collagen. GFP aggregated irreversibly with final concentrations of 0.5–4 μg/ml trypsin, 1.6–3.2 μM ADP, 2.5–5 μM epinephrine and 40 μl/ml soluble collagen. Addition of human fibrinogen to the Tyrode-suspending buffer Was required for ADP and epinephrine, but was not necessary for trypsin or collagen. Release of (¹⁴C)5HT was obtained with trypsin and collagen using the same concentrations as used in aggregation. GFP stored at room temperature for 48 h were still responsive to trypsin and collagen, whereas aggregability and (¹⁴C)5HT release induced by ADP and epinephrine were already impaired 5 h after collection of blood. CP-CPK, an ADP-removing reagent, blocked aggregation and release induced by low trypsin concentrations, suggesting that ADP plays an intermediate role in the mechanism by which trypsin activates platelets. Trypsin appears to be a valuable reagent for studying platelet physiology, particularly following storage.