TY  - JOUR
AU  - Fava, E.
AU  - Dehghany, J.
AU  - Ouwendijk, J.
AU  - Müller, A.
AU  - Niederlein, A.
AU  - Verkade, P.
AU  - Meyer-Hermann, M.
AU  - Solimena, M.
TI  - Novel standards in the measurement of rat insulin granules combining electron microscopy, high-content image analysis and in silico modelling.
JO  - Diabetologia
VL  - 55
IS  - 4
SN  - 0012-186X
CY  - Heidelberg
PB  - Springer
M1  - DZNE-2020-07522
SP  - 1013-1023
PY  - 2012
AB  - Knowledge of number, size and content of insulin secretory granules is pivotal for understanding the physiology of pancreatic beta cells. Here we re-evaluated key structural features of rat beta cells, including insulin granule size, number and distribution as well as cell size.Electron micrographs of rat beta cells fixed either chemically or by high-pressure freezing were compared using a high-content analysis approach. These data were used to develop three-dimensional in silico beta cell models, the slicing of which would reproduce the experimental datasets.As previously reported, chemically fixed insulin secretory granules appeared as hollow spheres with a mean diameter of ∼350 nm. Remarkably, most granules fixed by high-pressure freezing lacked the characteristic halo between the dense core and the limiting membrane and were smaller than their chemically fixed counterparts. Based on our analyses, we conclude that the mean diameter of rat insulin secretory granules is 243 nm, corresponding to a surface area of 0.19 μm(2). Rat beta cells have a mean volume of 763 μm(3) and contain 5,000-6,000 granules.A major reason for the lower mean granule number/rat beta cell relative to previous accounts is a reduced estimation of the mean beta cell volume. These findings imply that each granule contains about twofold more insulin, while its exocytosis increases membrane capacitance about twofold less than assumed previously. Our integrated approach defines new standards for quantitative image analysis of beta cells and could be applied to other cellular systems.
KW  - Animals
KW  - Cells, Cultured
KW  - Cytoplasmic Granules: metabolism
KW  - Cytoplasmic Granules: ultrastructure
KW  - Female
KW  - Insulin: metabolism
KW  - Insulin-Secreting Cells: metabolism
KW  - Insulin-Secreting Cells: ultrastructure
KW  - Microscopy, Electron, Transmission
KW  - Rats
KW  - Rats, Wistar
KW  - Secretory Vesicles: metabolism
KW  - Secretory Vesicles: ultrastructure
KW  - Insulin (NLM Chemicals)
LB  - PUB:(DE-HGF)16
C6  - pmid:22252472
C2  - pmc:PMC3296007
DO  - DOI:10.1007/s00125-011-2438-4
UR  - https://pub.dzne.de/record/141200
ER  -