Sequestration of serotonin in stored platelets.

A high-pressure liquid chromatographic procedure was used for the determination of 5-hydroxytryptamine (serotonin, 5HT) in platelets. The method, which is based on the separation on a reverse-phase column and measurement of native fluorescence in an acidified mobile phase, had a detection limit of femtomol quantities of 5HT. The mean contents of 5HT extracted from the Triton X-100-lysed platelets in random-donor platelet concentrates (PCs) were 0.39 +/- 0.19 mumol per 10(11) platelets (n = 5), the value of which was almost equal to 0.40 +/- 0.09 mumol per 10(11) platelets (n = 15) of platelets prepared by cytapheresis. The fate of platelet 5HT during storage of PCs at 22 degrees C with agitation was investigated for 5 days. Nearly all amounts of 5HT were sequestered within platelets after 5-day storage. No increased amounts of major metabolites of 5HT, 5-hydroxytryptophol and 5-hydroxy-3-indoleacetic acid, were detected in plasma. These data suggest that 5HT stored in dense granules of platelets is not metabolized during storage of PCs at 22 degrees C for 5 days.