Platelet storage: changes in cytosolic Ca2+ actin polymerization and shape

Abstract

Platelets gradually lose their disc shape during storage. The authors studied simultaneous changes in platelet cytosolic Ca2+ (Cai) and the polymerization state of actin as related to the shape. Platelet concentrates were stored under blood bank conditions for up to 10 days. Aliquots were removed and analyzed as follows: platelet Cai and increments in Cai induced by adenosine diphosphate (ADP) were determined by fluorescence of fura-2-loaded cells; loss of disc shape was determined by differences in light scattering intensity induced by stirring; and the ratio of globular and total actin (G/T) of platelets in plasma was determined by a modification of the DNase inhibition assay. Globular actin was found to be 86 +/- 3% of total actin in freshly drawn platelets suspended in plasma. The following changes occurred during storage: G/T in platelet concentrates increased from 63 +/- 5 (day 0) to 74 +/- 2% in the first 24 hours then fell to 33 +/- 6% by day 10. The percent discoid platelets also increased from day 0 to day 1 then fell in the ensuing days. There was an initial drop in Cai from day 0 to day 1, after which Cai increased on days 3 and 6. Globular actin polymerization during storage closely correlated with the change in percent discs (r = 0.95). During 6 days of storage Cai was highly correlated with shape change (r = 0.97) and to a lesser extent (r = 0.87) with the ratio of globular actin. The authors conclude that actin polymerization, shape, and Ca2+ change in a related fashion during storage.

Influence of a 12‐hour, 22°C holding period for buffy coats on the preparation of platelet concentrates stored in plasma

“…It is noteworthy that we detected no p-TG release in BC-PCs after 3 minutes of stimulation with agonist concentrations that led to significant release from fresh platelet^.^' Low p-TG release (10%) was detected only after longer activation times, as previously reported.,* Thus, since granule content was well maintained, the mechanism responsible for the release reaction during aggregation may be disturbed during storage. 29 We have obtained similar results in all tests measuring platelet activation and function with PCs prepared by the plasma-rich platelet method (not shown).…”

Translation of glycoprotein IIIa in stored blood platelets

“…35 Actin, a major component of the cytoskeleton, showed no change in its total amount in both studies, but revealed a shift toward more acidic isoforms during PLT storage. 36,37 [ 35 S]Methionine labeling, however, suggests that actin may be constitutively translated during PLT storage. Full-length b-actin mRNA was not well conserved in stored PLTs and showed a half-life of roughly 1.9 days (unpublished observations).…”

Loss of phospholipid asymmetry in human platelet plasma membrane after 1–12 days of storage

“…Thus, > 9-day-old platelets that had already shed vesicles in the storage bag had also undergone actin polymerization and produced filopods. These platelets contained 60% F-actin and a high intracellular calcium concentration [41]. This suggests that subsequent stimulation by calcium ionophore A23187 would have no effect on actin polymerization and therefore on morphological modifications in aged platelet membranes.…”

“…As discussed earlier [4], it is unlikely that a scrambling phenomenon was responsible for the rapid outflux of aminoPLs without any symmetrical Pam(dox)-GroPCho influx during fresh platelet activation. Activation of fresh platelets was associated with F-actin polymerization [41] in the presence of high calcium concentrations and with a large increase in the ratio of the outsidehnside plasma membrane areas [42] due to filopod formation. This ratio could in turn induce rapid massive outflux of aminoPLs to re-equilibrate the PL distribution.…”