Value of calcium and phosphate in a bicarbonate-containing platelet additive solution with low plasma levels in maintaining key in vitro platelet storage parameters

BACKGROUND: Use of recently developed platelet (PLT) additive solutions (PAS) with 5% plasma levels may reduce the frequency and/or severity of transfusion reactions attributed to plasma. PLTs suspended in bicarbonate-containing PAS-5 with 5% plasma levels can maintain key PLT parameters during 7-day storage. This study evaluates the role of calcium and phosphate, as constituents of PAS-5, in maintaining PLT parameters. STUDY DESIGN AND METHODS: An Amicus apheresis PLTunit (n = 13) was equally divided into four 60-mL aliquots in CF-250 polyolefin bags. Four different formulations of PAS-5 were prepared: PAS-5, PAS-5 without phosphate (-PO4), PAS-5 without calcium (-Ca), and PAS-5 without Ca and phosphate (-Ca/-PO4). PLTs were centrifuged, and the supernatant was expressed and replaced with the respective PAS, yielding PLTs suspended in 95% PAS and 5% plasma. PLTs were stored at 20 to 24 degrees C with agitation for 7 days. PLT in vitro parameters were evaluated on Days 1, 5, and 7. RESULTS: In PLT PAS-5 aliquots, pH levels were maintained better compared with those in -Ca and -Ca/-PO4 aliquots. Glycolysis was greater in -Ca and -Ca/-PO4 PLTaliquots compared with PAS-5 aliquots. Hypotonic stress response and morphology were less and p-selectin (CD62P) binding was greater in -Ca/-PO4 PLTaliquots. The accumulation of reactive oxygen species was greater in -Ca/-PO4 PLTs. Phosphorylation of p38 mitogen-activated protein kinase (MAPK) was greater in -Ca and -Ca/-PO4 PLTaliquots during storage. CONCLUSION: The removal of calcium and phosphate from PAS-5 leads to the activation of p38 MAPK and deterioration of key PLT storage parameters.