Platelet Shape Change: Induction by Trypsin and Release of an Acidic Macroglycopeptide from Washed Human Platelets and from those of Three Cases of Glanzmann’s Thrombasthenia

Abstract

Trypsin, which induced a rapid shape change followed by a large irreversible aggregation in gel-filtered control human platelets, induced an apparently normal shape change but no aggregation in gel-filtered thrombasthenic platelets. Addition of soybean trypsin inhibitor after the induction of the shape change in gel-filtered control platelets inhibited both further shape change and subsequent aggregation. Rapid release of an acidic macroglycopeptide was induced by trypsin from both control and thrombasthenic washed platelet suspensions with a significant part of the release occurring in a time scale parallel with the trypsin-induced shape change. The macroglycopeptide, which contained most of the released sialic acid, was derived from the largest of the native platelet membrane glycoproteins which is probably the major sialylglycoprotein of the platelet membrane.