Summary
The effects of phospholipids on calcium uptake by human platelets were investigated
utilizing 45CaCl2. Among the phospholipids tested, cardiolipin and phosphatidic acid exerted a significant
increase of calcium uptake by platelets. Calcium uptake was dependent upon cardiolipin
concentration and incubation time. These phospholipids enhanced platelet aggregation
induced by ADP (2 μM) or epinephrine (0.5 μg/ml). Cardiolipin caused the significant
release of serotonin from platelets in the absence of externally added calcium in
the medium.
These results may suggest that phospholipids activate platelets through their ionophoretic
activities.