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Secretory granules of insulin-secreting cells are used to store and release peptide hormones as well as low-molecular-weight compounds such as nucleotides. Here we have compared the rate of exocytosis with the time courses of nucleotide and peptide release by a combination of capacitance measurements, electrophysiological detection of ATP release and single-granule imaging. We demonstrate that the release of nucleotides and peptides is delayed by approximately 0.1 and approximately 2 seconds with respect to membrane fusion, respectively. We further show that in up to 70% of the cases exocytosis does not result in significant release of the peptide cargo, likely because of a mechanism that leads to premature closure of the fusion pore. Release of nucleotides and protons occurred regardless of whether peptides were secreted or not. These observations suggest that insulin-secreting cells are able to use the same secretory vesicles to release small molecules either alone or together with the peptide hormone.

Original publication




Journal article


J Cell Sci

Publication Date





4271 - 4282


Adenine Nucleotides, Adenosine Triphosphate, Amyloid, Cells, Cultured, Exocytosis, Hydrogen-Ion Concentration, Insulin, Insulin Secretion, Islet Amyloid Polypeptide, Islets of Langerhans, Membrane Potentials, Peptides, Receptors, Purinergic P2, Receptors, Purinergic P2X2, Secretory Vesicles, Time Factors, Transfection