Chemical Identity

Gastrin-17 (Primary Form)

Property	Value
Name	Gastrin-17
Gene	GAST (chromosome 17q21)
Sequence	Glu-Gly-Pro-Trp-Leu-Glu-Glu-Glu-Glu-Glu-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH₂
Length	17 amino acids
C-terminal	Amidated
PDB Structures	1NF9 (NMR)

Gastrin Isoforms

Isoform	Length	Source	Potency
Gastrin-14	14 aa	Antrum	High
Gastrin-17	17 aa	Antrum (dominant)	Highest
Gastrin-34	34 aa	Duodenum	Lower

Receptor

CCK-B/Gastrin Receptor (CCK2R)

• Gene: CCKBR (chromosome 11p15.4)
• Expression: Gastric parietal cells, ECL cells, brain
• Affinity: Binds both gastrin and CCK-8

Physiological Functions

Gastric Acid Secretion

Protein meal → G-cells (antrum) → Gastrin release
    → CCK-B receptor (ECL cells) → Histamine release
    → H2 receptor (parietal cells) → Gastric acid secretion

Other Functions

• Mucosal growth: Trophic effect on gastric mucosa
• Pancreatic enzymes: Stimulates secretion
• Lower esophageal sphincter: Contracts sphincter

Clinical Significance

Zollinger-Ellison Syndrome

• Gastrinoma: Gastrin-secreting neuroendocrine tumor
• Symptoms: Severe peptic ulcers, diarrhea, gastric acid hypersecretion
• Diagnosis: Fasting gastrin >1000 pg/mL
• Treatment: Proton pump inhibitors (PPIs), surgery

Gastrin as Biomarker

• Serum gastrin: Diagnosis of gastrinoma
• Gastrin stimulation test: Assesses ECL cell function

Manufacturing

• SPPS (Fmoc): Standard solid-phase synthesis
• C-terminal amidation: Required for activity
• Purification: RP-HPLC

References

1. Edkins JS. “On the chemical regulation of gastric secretion.” Journal of Physiology 23:147-162, 1905.
2. Gregory RA, Tracy HJ. “Isolation of two gastrins from human antral mucosa.” Nature 257:322-323, 1975.
3. Walsh JH. “Gastrin.” Gut 35:S1-S5, 1994.
4. Dockray GJ, et al. “Gastrin and CCK receptors.” Gut 42:740-745, 1998.
5. Jensen RT, et al. “Gastrinomas and the Zollinger-Ellison syndrome.” Seminars in Gastrointestinal Disease 6:166-177, 1995.