glucagon secretion

Definition

Target type: biologicalprocess

The regulated release of glucagon from secretory granules in the A (alpha) cells of the pancreas (islets of Langerhans). [GOC:BHF, GOC:rl]

Glucagon secretion is a complex process regulated by blood glucose levels, initiated by the alpha cells of the pancreas. When blood glucose levels fall below a certain threshold, the alpha cells detect this drop and trigger the release of glucagon. This hormone then travels through the bloodstream and primarily targets the liver, promoting the breakdown of glycogen into glucose and releasing it into the bloodstream, ultimately raising blood sugar levels.

Here's a breakdown of the process:

1. **Detection of low blood glucose:** Alpha cells in the pancreatic islets of Langerhans possess specialized receptors that sense low blood glucose concentrations.

2. **Signal transduction cascade:** This low glucose signal activates a cascade of intracellular events within the alpha cells, involving G-protein coupled receptors, adenylate cyclase, and cAMP.

3. **Glucagon synthesis and storage:** Alpha cells continuously synthesize and store glucagon in secretory granules.

4. **Exocytosis:** The increased intracellular cAMP triggers the fusion of these granules with the alpha cell membrane, releasing glucagon into the bloodstream through exocytosis.

5. **Glucagon binding to liver cells:** Glucagon circulates in the blood and binds to specific receptors on the surface of liver cells (hepatocytes).

6. **Glycogenolysis:** This binding activates a signaling pathway within the hepatocytes, leading to the breakdown of stored glycogen (a complex carbohydrate) into glucose.

7. **Glucose release:** The released glucose enters the bloodstream, increasing blood sugar levels.

8. **Negative feedback:** As blood glucose levels rise, the secretion of glucagon is suppressed, maintaining a homeostatic balance in blood sugar levels.

In summary, glucagon secretion is a carefully regulated hormonal response to low blood glucose, ensuring that the body has a readily available source of energy during periods of hypoglycemia.'
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Proteins (1)

Compounds (2)