Role of acetate during platelet storage in a synthetic medium

It has previously been shown that buffy coat platelet concentrates (BC- PCs) stored in a medium made up of approximately 70 percent platelet storage medium (Plasma-Lyte A, PL) and 30 percent plasma (BC-PC-P) are effective in vivo after 9 to 12 days of storage. In addition to sodium, potassium, magnesium, and chloride, PL contains 27 mM (27 mmol/L) sodium acetate and 23 mM (23 mmol/L) sodium gluconate. This study investigated the effect of acetate and gluconate on platelet metabolism. Identical BC-PCs were stored at 22 ± 2°C in PL (BC-PC-P); PL with gluconate but without acetate, termed PL- A (BC-PC-A); or PL with acetate but without gluconate, termed PL-G (BC-PC-G). On Day 1 of storage, no significant differences were seen between the three groups of BC-PCs. In both BC-PC-P and BC-PC-G, pH and bicarbonate were stable at 7.0 ± 0.03 and 8.4 ± 0.9 mEq per L throughout 10 days of storage, whereas in BC-PC-A, they fell to 6.7 ± 0.05 and 5.5 ± 0.8 mEq per L on Day 5 (p <0.01 vs. Day 1) and to 6.1 ± 0.1 and 1.2 ± 0.4 mEq per L, respectively, on Day 10. The buffering capacities of 70 percent PL, PL-A, or PL-G and 30 percent plasma were similar in a platelet-free setting when incremental additions of lactic acid were made. The role of acetate was further studied by adding ¹⁴C- or ³H-labeled acetate to BC-PC-P. On Day 7 of storage, radioactivity decreased to 79 ± 1 percent of baseline in ¹⁴C- labeled BC-PC-P (p = 0.02), while it was unchanged in ³H-labeled BC-PC-P and in control samples in which ¹⁴C- and ³H-acetate were added to platelet- free plasma or PL. These studies indicate that platelets metabolize acetate to CO₂ during storage and that acetate metabolism plays a major role in pH control during storage of BC-PCs.