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ludc web

Lena Eliasson

Principal investigator

ludc web

Fast insulin secretion reflects exocytosis of docked granules in mouse pancreatic B-cells.

Author

  • Charlotta Olofsson
  • Sven Göpel
  • Sebastian Barg
  • Juris Galvanovskis
  • Xiaosong Ma
  • Albert Salehi
  • Patrik Rorsman
  • Lena Eliasson

Summary, in English

A readily releasable pool (RRP) of granules has been proposed to underlie the first phase of insulin secretion. In the present study we combined electron microscopy, insulin secretion measurements and recordings of cell capacitance in an attempt to define this pool ultrastructurally. Mouse pancreatic B-cells contain approximately 9,000 granules, of which 7% are docked below the plasma membrane. The number of docked granules was reduced by 30% (200 granules) during 10 min stimulation with high K+. This stimulus depolarized the cell to -10 mV, elevated cytosolic [Ca2+] ([Ca2+](i)) from a basal concentration of 130 nM to a peak of 1.3 microM and released 0.5 ng insulin/islet, corresponding to 200-300 granules/cell. The Ca2+ transient decayed towards the prestimulatory concentration within approximately 200 s, presumably reflecting Ca2+ channel inactivation. Renewed stimulation with high K+ failed to stimulate insulin secretion when applied in the absence of glucose. The size of the RRP, derived from the insulin measurements, is similar to that estimated from the increase in cell capacitance elicited by photolytic release of caged Ca2+. We propose that the RRP represents a subset of the docked pool of granules and that replenishment of RRP can be accounted for largely by chemical modification of granules already in place or situated close to the plasma membrane.

Department/s

  • Faculty of Medicine
  • Department of Experimental Medical Science
  • Diabetes - Islet Cell Exocytosis

Publishing year

2002

Language

English

Pages

43-51

Publication/Series

Pflügers Archiv

Volume

444

Issue

1-2

Document type

Journal article

Publisher

Springer

Topic

  • Endocrinology and Diabetes

Status

Published

Research group

  • Diabetes - Islet Cell Exocytosis

ISBN/ISSN/Other

  • ISSN: 0031-6768