Variation of the Proelastase/Elastase Ratio in Human Blood Platelet Populations

Human blood platelets have been separated into four populations according to their density, and the elastase activity measured in the presence and absence of trypsin in each of the four populations. Trypsin dependent elastolytic activity (proelastase) was higher in heavy (C and D) than in light (A and B) platelets, whereas trypsin independent elastolytic activity (elastase) was higher in light than in heavy platelets. The proelastase is presumably activated into fully active elastase as the platelet becomes lighter by an endogenous activating system.