STORAGE LESION OF HUMAN PLATELETS AS REVEALED BY ULTRATHIN SECTIONS AND FREEZE-FRACTURE REPLICAS

We report the ultrastructural changes occurring in human platelets dur ing eight days of storage. Extension of pseudopodia is frequently obse rved, but a concentration of organelles in the centre of the platelets is found only in a minor fraction (similar to 5%). Striking changes c an be observed in both the granules and the open canalicular system. I n fresh platelets, the latter often has the form of stacked membranes that have no lumen, but these membranes separate and spread with incre asing storage time. However, the openings of this system on the outer surface of the platelet remain unchanged. Some of these features diffe r from the morphological description of platelets activated by thrombi n or ADP, and suggest that the storage lesion is the result of a prolo nged weak activation that leads to an incomplete release reaction with in the first five days.