The swirling phenomenon in stored platelets is influenced by their endogenous serotonin

The presence of the swirling phenomenon is useful to define platelet concen trates that are suitable for transfusion. If it is possible to identify don or-related factors which are related to persisting swirling during storage, it is possible to select platelet donors. Endogenous platelet serotonin co ntent is stable and easily measured and related to agonist-induced serotoni n secretion. During a 3-month period, the swirling in 825 single donor platelet concentr ates was controlled before issue. Endogenous serotonin, % serotonin release and swirling were tested in 21 concentrates with poor or no swirling durin g storage. Sixty-three concentrates were randomly selected from the routine ly prepared platelet concentrates and were routinely tested with the same a nalyses on days 1 and 7. To evaluate an obvious effect of endogenous seroto nin on the swirling phenomenon, eight platelet concentrates prepared from b uffy coat, each from four donors, were divided. One part was stored in the presence of 8.5 mu mol serotonin L-1, and analysed as the control concentra tes. The endogenous serotonin content in the 'low-swirling' concentrates was sig nificantly lower than in the control group (P<0.001). PCO2 and pH were sign ificantly lower, and PO2 and MPV significantly higher than in the controls. In the control group, swirling after 7 days was significantly correlated w ith serotonin release. In the eight buffy-coat concentrates enriched in end ogenous serotonin, both swirling and the percentage serotonin release were improved after storage for 10 days, compared with nonenriched concentrates. This study suggests that endogenous serotonin content and serotonin release are factors that may be of significance concerning preservation of the swi rling phenomenon in platelet concentrates during storage.