PHOSPHOLIPID LOSS IN DYING PLATELETS

The death of a cell results in a large amount of membrane lipid, predo minantly phospholipids and cholesterol, that must be eliminated. In th is study, we have examined what happens to phospholipids in dying rat platelets. Rat platelets were incubated for up to three days following their activation with thrombin. Platelet death occurred during the fi rst day of incubation. This was indicated by a complete loss of platel et lactate dehydrogenase into the incubation medium. The platelets pro gressively lost over one-half of their phospholipid content during the three days of incubation. Cholesterol and sphingomyelin (the phosphol ipid with the highest affinity for cholesterol) were not lost during t he same period. Our findings suggest that significant degradation of c ellular non-sphingomyelin phospholipid can be triggered by cell death. The preservation of sphingomyelin in dying platelets, may be an adapt ive response to maintain cholesterol in a solubilized state within dyi ng cells.