Gastrin is not directly present in the diet, but dietary protein intake is a factor in triggering the production of gastrin, which stimulates gastric acid secretion. Gastrin, a hormone, induces specialized parietal cells in the lining of the stomach, called G cells, to secrete a gastric acid called hydrochloric acid, which aids digestion. Although dietary protein can initiate gastrin production, a number of other factors, such as distension of the stomach, elevated calcium levels and vagus nerve stimulation, also influence production.
Gastrin Function
Special cells in the stomach and pancreas create and reserve gastrin. It helps the digestion of food, especially proteins, by activating the secretion of gastric acid. Stimulation of the vagus nerve, a response to the stomach being stretched, also promotes gastrin production and acid secretion. Gastrin activates the release of pancreatic and stomach enzymes, increases the movement of stomach and intestinal contents and initiates the flow of bile from the liver. The secretion of gastric acid is higher during the night, consequently those who take medications to inhibit acid production do so at night.
Negative Feedback System
When food enters the stomach, gastric acid in the stomach increases, food products break down, acid levels decrease and the negative feedback system activates. Negative feedback regulates acid secretions by the production of somatostatin, a neurohormone. Somatostatin, produced by D cells in the stomach lining, blocks gastrin and further acid production in response to high acid levels correlating to a pH less than three. The normal consequence of the feedback system helps maintain limited to modest amounts of gastrin in the bloodstream.
Gastric Acid Conditions
Zollinger-Ellison syndrome, a rare condition, causes a disproportionate amount of gastrin and gastric acid production. Zollinger-Ellison syndrome is identified by elevated gastrin concentrations, a considerably larger production of gastric acid and peptic ulcers. The syndrome is caused by tumors, called gastrinomas, which secrete large amounts of gastrin. The tumors can occur in the stomach, pancreas and the duodenum and are frequently malignant. Duodenal ulcers might result from high levels of gastric acid secretions, the presence of Helicobacter pylori bacteria and overuse of NSAIDS.
Gastrin Test
The gastrin test requires a blood sample and a 12-hour fast from food and fluids. In addition, avoiding alcohol consumption for 24 hours is required to ensure accurate results. Some drugs, such as belladonna, insulin and atropine, hamper test results. Stress and excessive exercise also interfere with test results by increasing gastrin levels, but 30 minutes of relaxation before the test might alleviate false results. Consult your physician concerning restrictions on medications before your test.
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