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Insulin-stimulated insulin secretion in single pancreatic beta cells
C A Aspinwall1, J R Lakey, R T Kennedy
1Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, USA.
The Journal of Biological Chemistry
|February 26, 1999
Summary
Insulin receptors in pancreatic beta cells trigger insulin secretion via a positive feedback loop. This autocrine action links insulin resistance to impaired insulin secretion.
Area of Science:
- Endocrinology
- Cell Biology
- Diabetes Research
Background:
- Functional insulin receptors are present in pancreatic beta cells.
- The specific physiological roles of these receptors beyond insulin synthesis remain largely unknown.
Purpose of the Study:
- To investigate the direct physiological effects of insulin on pancreatic beta cells.
- To determine the role of the beta cell insulin receptor in insulin secretion and its potential autocrine functions.
Main Methods:
- Amperometric measurements were performed on single, primary pancreatic beta cells.
- Exogenous insulin was applied to assess its effects on exocytosis and intracellular calcium levels.
- Insulin receptor function was modulated using blocking agents or by reducing free insulin concentrations.
Main Results:
- Insulin application evoked exocytosis mediated by the beta cell insulin receptor.
- Insulin increased intracellular Ca2+ concentration but minimally affected membrane potential.
- Blocking the insulin receptor or reducing free insulin diminished secretion induced by other secretagogues, indicating autocrine action.
Conclusions:
- The beta cell insulin receptor mediates positive feedback for insulin secretion.
- This autocrine mechanism provides a potential link between insulin resistance and impaired insulin secretion in diabetes.