Resin-packed nanoelectrospray in combination with video and mass spectrometry for the direct and real-time molecular analysis of mast cells

A nano-electrospray ionization (nanoESI) emitter for analysis of a biological solution was developed by packing a nanoESI needle with two types of resins for desalting and preconcentration of target molecules. Determination of secreted histamine and serotonin molecules in cell culture buffers was demonstrated using 5-methyltryptamine as internal standard. The results showed good linearity of target signals in the concentration range from 0.25 to 50.0 ng/mL of histamine or serotonin. These molecules were monitored to be secreted by A23187 (calcium ionophore) stimulant in rat peritoneal mast cells. Using a combination of a video-microscope and a mass spectrometer, we could visualize exocytotic moments and analyze secreted molecules by mass spectrometry simultaneously. Time-dependent release of histamine and serotonin from activated mast cells showed that significant production of these molecules occurred and reached a maximal level at 15 min for serotonin and at 30 min for histamine, respectively. These results showed that this method allows the direct and timely analysis of secreted molecules in biological responses.