Is insulin released through exocytosis?

Insulin is stored in large dense core vesicles and released by exocytosis, a multistage process involving transport of vesicles to the plasma membrane, their docking, priming and finally their fusion with the plasma membrane.

Does exocytosis secrete insulin from the pancreas?

Insulin secretion from pancreatic B-cells Like in other endocrine cells and in neurones, exocytosis in B-cells is regulated and the amount of insulin circulating in the blood depends more on the rate of exocytosis than on the rate of insulin biosynthesis.

Is insulin secreted through endocytosis?

Insulin secretion is regulated at various stages including synthesis, exocytosis, and endocytosis. Endocytosis is a fundamental stage to replenish insulin to the secretory vesicles after insulin secretion and to maintain constant β-cell volume before and after insulin secretion.

What stimulates insulin secretion?

Proteins in food and other hormones produced by the gut in response to food also stimulate insulin release. Hormones released in times of acute stress, such as adrenaline, stop the release of insulin, leading to higher blood glucose levels to help cope with the stressful event.

How does exocytosis lead to the secretion of insulin?

The resulting increase in the cytosolic ATP/ADP‐ratio closes K ATP ‐channels in the plasma membrane, which leads to depolarization of the cell and influx of Ca 2+ through voltage dependent L‐type Ca 2+ ‐channels (VDCC). The increase in Ca 2+ at the granule then triggers exocytosis and thus insulin secretion.

How is the rate of exocytosis in B ‐ cells regulated?

Like in other endocrine cells and in neurones, exocytosis in B‐cells is regulated and the amount of insulin circulating in the blood depends more on the rate of exocytosis than on the rate of insulin biosynthesis. B‐cells are electrically active and respond to elevated blood glucose by generating action potentials (fig. 1).

How are hormones stored and released during exocytosis?

These hormones are stored in secretory granules and released by exocytosis when signals are received. When glucose concentration in the blood is too high, insulin is released from islet beta cells causing cells and tissues to take up glucose from the blood. When glucose concentrations are low, glucagon is secreted from islet alpha cells.

How does insulin secretion occur in the B cell?

The increase in Ca 2+ at the granule then triggers exocytosis and thus insulin secretion. Sulfonylurea close the K ATP ‐channel by binding to its SUR‐subunits, and thereby cause membrane depolarization independent of the metabolic state of the cell. B‐cells are fairly typical examples of peptide‐secreting endocrine cells.