Demonstration and evaluation of apparent cytoplasmic and vesicular serotonin compartments in human platelets

Thrombin has been used in conjunction with formaldehyde treatment to investigate the distribution of labeled serotonin between releasable and non-releasable compartments during the serotonin uptake process. The data indicate that serotonin accumulates in a predictable fashion in both compartments, which may represent, respectively, vesicular and cytoplasmic amine pools. The results also suggest that the cytoplasmic pool may reach sizable proportions under certain incubation conditions.