What is Gastrina
Gastrin, or rather gastrins, are peptide hormones secreted by the cells of the gastric mucosa. More active in this sense are the lower regions of the stomach, such as the antrum and especially the pylorus.
The synthesis of gastrin is entrusted to some specialized cells, called G cells and also present in the mucosa of the duodenum (proximal tract of the small intestine, which follows the gastric pylorus for continuity). In pathological conditions, particular tumors of the pancreas and duodenum called gastrinomas, and their metastases, are the site of an "intense gastrin production, while in physiological situations the contribution of these two organs is modest.
Once secreted, the gastrin released into the blood returns to the stomach through the bloodstream and carries out its action on the parietal cells (responsible for the secretion of hydrochloric acid and intrinsic factor) and on the enterochromaffin cells (which secrete serotonin by stimulating the contractions of the gastric muscles) .
Functions
The secretion of gastrin occurs under the nerve impulse generated by the presence of food in the stomach. Alcohol, coffee, a gastric pH that is too high, the presence of peptides in the bolus (protein-rich meal) and the same effect have the same effect. hypercalcemia.
Gastrin is not deposited and released in its final form, but as a pre-pro-hormone, from whose metabolism the different isoforms originate.
Once released, gastrin stimulates the synthesis of digestive enzymes, water and salts by the stomach and pancreas; it also increases the blood flow to the stomach and stimulates the contractions necessary for the remixing of the chyme.
Gastrin is the main regulator of stomach acid secretion. It also performs an "important trophic function for the growth of the gastric mucosa.
Elevated gastrin concentrations stimulate insulin secretion, pepsinogen release by peptic cells and gallbladder filling; they also decrease the tone of the esophageal sphincter and favor the already mentioned development of the gastric mucosa.
Under normal conditions, hypergastrinemia is readily corrected through the classic feed-back mechanisms; thus, as soon as the gastric intraluminal pH is excessively lowered (<3), gastrin secretion is inhibited. The HCl, in fact, stimulates the release of somatostatin from the cells of the antrum, effectively inhibiting the secretion of gastrin and the release of histamine. Secretin, GIP (gastroinhibitory peptide), VIP, glucagon and calcitonin all have the same inhibitory effect.
High gastrin - hypergastrinemia
It has been shown that gastrin levels follow a trend inversely proportional to the parietal cell mass, therefore to the acid secretion.
Gastrinomas (Zollinger-Ellison syndrome) cause "acid hypersecretion that affects the appearance of peptic ulcers (especially duodenal) that are recurrent and / or resistant to drug treatment, with diarrhea responsive to proton pump inhibitors and with esophageal reflux disease. , in these cases, they can also lead to severe complications, such as perforation and haemorrhage.
Autoimmune atrophic gastritis is characterized by the attack of parietal cells by abnormal antibodies, resulting in hypochlorhydria (low gastric acidity) and pernicious anemia. High blood concentrations of gastrin can thus be appreciated, secreted conspicuously in an attempt to correct the reduced gastric acidity.
Mild hypergastrinemia can also occur in the presence of Heliobacter pylori or following the use of drugs capable of reducing gastric acidity.
In type IV mucolipidosis very high concentrations of gastrin are recorded due to the achlorhydria caused by this neurogenic disorder.
Gastrinemia »
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