Glucagon Diabetes mellitus Islet microcirculation

Isolated α-cell
• Insulin receptor transcript was relatively abundant in α-
cells, similar to liver
α-Cells are also important sites of insulin action
• Transcript for GLP-1 receptor was not detected in α-cells
nor did GLP-1 stimulate α-cell glucagon release
in agreement with earlier studies:
– cAMP levels in α-cells were unaffected by GLP-1
– type 1 DM : GLP-1 had no effect on plasma glucagon levels
during hyperinsulinemic-euglycemic clamp
• Apparent direct inhibition by GLP-1 on glucagon secretion
: paracrine factors may have mediated the suppression
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Glucagon secretion from in situ–perfused rat pancreas
Membrane potential recording from an isolated α-cell
using the perforated-patch whole-cell configuration
Data are mean+SE of six independent perfusions
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The recording is typical of six cells.
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Electrical activity in response to “Zn-free" insulin was
analyzed and the effect on spike frequency calculated
Glucagon secretion from isolated α-cells
Data are mean+ SE of six experiments
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mean+SE *P < 0.05, **P < 0.005
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