Storage of platelets in additive solutions: effects of phosphate

In a previous study, low adenine nucleotide levels and a reduced rate of glycolysis were found in platelet concentrates (PCs) prepared by apheresis and stored in a platelet additive solution (PAS). Our objective was to investigate whether the use of PAS with or without phosphate can influence platelet metabolism in a similar way.

The in vitro effects of storage in either plasma or a PAS (T-Sol or PAS-III, both containing citrate, acetate and sodium chloride, PAS-III containing also phosphate) of buffy-coat-derived pooled platelet concentrates (BC-PCs) and apheresis platelets were investigated. The use of PAS implies inclusion of some plasma (20 or 35%). Paired studies over 7 days included investigation of cell counts, pH, PO2, PCO2, bicarbonate, glucose, lactate, adenine nucleotides, and extracellular adenylate kinase activity as a marker for disintegration of platelets. The expected concentration of phosphate in T-Sol is 0.6-1.8 mmol/l (with CPD plasma) and 0.2-0.6 mmol/l (with ACD plasma), and in PAS-III, 15-25 mmol/l (calculated values).

BC-PCs were compared during storage in 35% CPD plasma and 65% PAS (T-Sol or PAS-III) (experiment 1), or alternatively 20% CPD plasma and 80% PAS (T-Sol or PAS-III) (experiment 3). In both studies, PAS-III shows similar and significantly higher rates of glycolysis in terms of consumption of glucose (0.06 vs. 0.04 mmol/day/10(11) platelets) and production of lactate (0.11 vs. 0.07 mmol/day/10(11) platelets) compared with T-Sol. Levels of pH and adenine nucleotides were similar when 35% plasma was used. With only 20% plasma, significantly higher levels of adenine nucleotides were found with PAS-III compared to T-Sol. The storage of apheresis platelets in 35% ACD plasma and 65% PAS (either T-Sol or PAS-III) (experiment 5) gave significantly higher values for PAS-III compared to T-Sol with regard to consumption of glucose (0.08 vs. 0.06 mmol/day/10(11) platelets), production of lactate (0.14 vs. 0.11 mmol/day/10(11) platelets) and adenine nucleotide levels.

With respect to apheresis PCs stored in media containing ACD plasma, our results suggest that the differences found are related to the concentration of phosphate. The results for BC-PCs stored in media containing CPD plasma suggest that PAS-III is preferable to T-Sol as the PAS at plasma concentrations below 35%. The mechanism behind the phenomena observed with BC-PCs is not known.