Monitoring Exocytosis and Release from Individual Mast Cells by Capillary Electrophoresis with Laser-Induced Native Fluorescence Detection

The complex temporal evolution of on-column exocytotic
release of serotonin and proteins from individual rat
peritoneal mast cells (RPMCs) was monitored by using
capillary electrophoresis. Laser-induced native
fluorescence detection with 275-nm excitation was used, and a
detection limit of 1.7 amol (S/N = 3; rms) was obtained
for serotonin. A physiological running buffer was
used
to ensure that the cell remained viable throughout.
The
secretagogue was polymyxin B sulfate (Pmx). Following
the injection of a single mast cell into the capillary,
electromigration of Pmx toward and past the cell induced
degranulation and release of serotonin. The time
course
of release was registered in the electropherograms with
subsecond resolution. Subsequent introduction of SDS
caused the cell to lyse completely and allowed the
residual
serotonin to be quantified. The average amount of
serotonin observed per RPMC was 1.6 ± 0.6 fmol; the average
percentage of serotonin released was 28 ± 14%.
Events
that are consistent with released serotonin from single
submicrometer granules (250 aL each) were evident, each
of which contained an average amount of 5.9 ± 3 amol.