Efflux of granule constituents from platelets exposed to different mechanical forces

The efflux of 14C-norepinephrine, 3H-serotonin and β-thromboglobulin from platelets was compared with the extent of lysis in two different systems of incubation, in which Ca²⁺ and conventional platelet activating agents were omitted. In the first system platelets were incubated in buffer at 37°C and gently shaken. Cell lysis was low and efflux of 14C-norepinephrine was 71–97% of total initial uptake after 24 hours. In the other system rotating plastic tubes at 20°C were used which exposed the platelets to higher mechanical stress. Cell lysis and aggregation was already high after 10–30 minutes, but the efflux of 14C-norepinephrine and 3H-serotonin was lower and not parallel to cell lysis. The release of 14C-norepinephrine was higher than that of 3H-serotonin in both systems. There was a considerable release of β-thromboglobulin from platelets remaining in plasma despite of a constant pH. These findings indicate that platelet lysis is independent of the release of platelet granule constituents.