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Updated: Apr 30, 2026

Glucose-Stimulated Insulin Secretion via Perfusion through the Mice Vasculature with an Intact Pancreas
Published on: July 25, 2025
Insulin secretion from beta cells in intact mouse islets is targeted towards the vasculature
Jiun T Low1, Michael Zavortink, Justin M Mitchell
1School of Biomedical Sciences, University of Queensland, St Lucia, QLD, 4072, Australia.
Aims/Hypothesis:
We set out to test the hypothesis that insulin secretion from beta cells is targeted towards the vasculature.
Methods:
The spatial location of granule fusion was identified by live-cell two-photon imaging of mouse pancreatic beta cells within intact islets, using sulforhodamine B labelling. Three-dimensional (3D) immunofluorescence of pancreatic slices was used to identify the location of proteins associated with neuronal synapses.
Results:
We demonstrated an asymmetric, non-random, distribution of sites of insulin granule fusion in response to glucose and focal targeting of insulin granule secretion to the beta cell membrane facing the vasculature. 3D immunofluorescence of islets showed that structural proteins, such as liprin, piccolo and Rab2-interacting molecule, normally associated with neuronal presynaptic targeting, were present in beta cells and enriched at the vascular face. In contrast, we found that syntaxin 1A and synaptosomal-associated protein 25 kDa (SNAP25) were relatively evenly distributed across the beta cells.
Conclusions/Interpretation:
Our results show that beta cells in situ, within intact islets, are polarised and target insulin secretion. This evidence for an 'endocrine synapse' has wide implications for our understanding of stimulus-secretion coupling in healthy islets and in disease.
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