Big gastrin

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big gastrin

Big gastrin is a peptide hormone that plays a crucial role in the digestive system by stimulating the secretion of gastric acid, which is necessary for the digestion of food in the stomach. It is one of the several forms of the hormone gastrin, with others being little gastrin and mini gastrin. Big gastrin is distinguished by its larger molecular size and longer peptide chain, consisting of 34 amino acid residues, hence it is often referred to as G-34.

Production and Structure

Big gastrin is produced by G cells in the antrum of the stomach, duodenum, and the pancreas. Its production is stimulated by the presence of partially digested proteins in the stomach, which signals the need for more gastric acid to continue the digestion process. The structure of big gastrin includes a sequence of 34 amino acids, with a biologically active C-terminus that is identical to that of little gastrin, allowing it to bind to and activate the gastrin receptor on the surface of gastric parietal cells.

Function

The primary function of big gastrin, along with other forms of gastrin, is to stimulate the parietal cells in the stomach lining to secrete gastric acid (HCl). This increase in gastric acid lowers the pH of the stomach, which is essential for the digestion and breakdown of proteins. Big gastrin also plays a role in stimulating the growth of the gastric mucosa and increasing the motility of the gastrointestinal tract, preparing it for the efficient processing of food.

Clinical Significance

Abnormally high levels of big gastrin can lead to conditions such as Zollinger-Ellison syndrome, a rare disorder characterized by the formation of gastrin-secreting tumors, which lead to excessive gastric acid production. This can result in recurrent peptic ulcers and can be diagnosed through the measurement of gastrin levels in the blood. Treatment often involves the use of proton pump inhibitors to reduce acid production and surgical removal of the tumors when possible.

Conversely, low levels of gastrin can indicate atrophic gastritis or other conditions leading to reduced gastric acid secretion, which can impair digestion and nutrient absorption.

See Also

• Gastrin
• Gastric acid
• Zollinger-Ellison syndrome
• Peptide hormone
• Gastrointestinal tract