Intra-extracellular Electroanalysis Reveals Vesicular Serotonin Release from Pancreatic Beta Cells is Not all or None

Recent work has shown that chemical release during the fundamental cellular process of exocytosis in model cell lines is not all or none. [1-2] We tested this theory for vesicular release from single pancreatic beta cells. The vesicles in these cells release insulin, but also serotonin, which is detectible with amperometric methods. [3-4] We amperometrically quantified the number of serotonin molecules stored inside of individual nanoscale vesicles (39317 ± 1611) in the cell cytoplasm before exocytosis and the number of serotonin molecules released from single cells (13310 ± 1127 molecules) for each exocytosis event during stimulated release. Thus, beta cells release only one-third of their content, clearly supporting partial release in this system. This is an important result as it contrasts that in most diabetes research involving exocytosis, it is assumed that exocytosis is all or none.