Summary
The preparation of human platelet membranes and their characterization by electron microscopy and their enzymatic, lipid and protein content is reported. The membranes can be prepared in good yield from about one unit of blood. Using both sucrose and Ficoll density gradients as controls to each other, constant and reproducible membrane preparations of comparable biochemical composition are obtained. Electron microscopy shows uniform membrane structures without other contaminating subcellular organelles. The membranes are characterized by the enrichment of the acid para-nitrophenylphosphatase, a low activity of granular enzymes and by proteins of molecular weights from 20.000 to more than 100.000. They show a high content of N-acetylneuraminic acid, cholesterol, phospholipids, and in particular a high percentage of sphingomyelin. This preparation can be used for metabolic tracer studies at a subcellular level.
