Morphological changes associated with pH changes during storage of platelet concentrates in first-generation 3-day container.

The platelet injury and loss of viability that has been shown to occur with storage of platelet concentrates (PC) under conditions with increasing or falling pH were examined using scanning and transmission electron microscopy. After storage, samples were taken for measurement of pH value, platelet count and size distribution, release of lactate dehydrogenase (LDH) into plasma, and for SEM and TEM. Increased levels of LDH were observed in PC with pH above 7.3 and below 6.1. In PC with pH above 7.3 this was related to an increased number (23%) of platelets that were lysed or had a swollen disintegrated internal structure (balloons) as seen with TEM. SEM and Coulter counter studies also showed that platelet fragmentation and formation of microvesicles were prominent in PC with pH above 7.3. The electron microscopic pictures confirmed previous suggestions that platelet disc-to-sphere transformation and cytoplasmic swelling occur when pH falls below 6.7-6.8 during storage. SEM studies showed that concomitant with this change, folds and bulky projections appeared on the platelet surface. In PC with pH below 6.1 the morphological change was irreversible with the appearance of more than 90% lysed and balloon platelets. In conclusion, these studies suggest that the loss of viability observed with PC with pH above 7.3 or below 6.1 after storage is related to an increased percentage of lysed and balloon platelets.