We studied extracellular accumulation in buffy-coat-derived platelet pools suspended in platelet additive solutions (PAS). 20 platelet pools were prepared from buffy coats of 60 donors and stored in either PAS I (n = 10) or PAS II (n = 10). Samples were drawn from the donors to determine the normal range of histamine, plasminogen activator inhibitor 1 (PAI-1), myeloperoxidase (MPO) and interleukin (IL)-6. After preparation samples were collected on days 0, 5 and 7 from the 20 platelet pools respectively, to determine extracellular accumulation of the same substances. Extracellular histamine, PAI-1 and MPO were detected in significant levels (P < 0.0001) immediately after preparation of the platelet pools. Only the extracellular level of PAI-1 increased significantly during storage from day 0 to day 7 (P < 0.01). After preparation and storage to day 7 IL-6 was found in only three of the 20 platelet pools.
Even though platelets were prepared by the buffy-coat method, to produce a low leucocyte count and thereby low cytokine (IL-6) content, there was still significant contamination by other bioactive substances.