Histamine H2 receptor

• OMIM: 142703
• UniProt: P25021

Histamine H2 receptor (short H2-receptor ) is a protein from the family of histamine receptors that can be activated by the body's own tissue hormone histamine. H2-receptors are involved in regulatory production of gastric juice. Stimulation of H2 receptors also results in about an acceleration of the heart beat and to an extension of small blood vessels. H2 - receptor antagonists ( H2 antihistamines ) such as cimetidine and ranitidine, inhibit the production of stomach acid and are used to treat gastric and duodenal ulcers used.

Biochemistry

Genetics

The H2 receptor in human was first cloned in 1991. It is encoded by a gene on chromosome 5 in the 5q35 locus. The coding DNA sequence is intro free.

Protein structure

The H2 - receptor protein in humans consists of 359 amino acids. As for many other receptors belonging to the family of G-protein -coupled receptors, a structure is adopted for the H2-receptor with seven transmembrane helical domains ( heptahelikaler receptor).

Signal transduction

At a molecular level resulting stimulation of H2 receptors to activation of G - proteins and as a result in activation of adenylyl cyclase. This activation of the adenylyl cyclase is connected to an accumulation of intracellular cAMP, and the release of Ca2 from intracellular stores. Moreover, H2 receptors regulate the activity of genes that play a role in cell proliferation and cell differentiation.

Function

The H2 receptor is critically involved in the regulation of gastric acid production. In addition, this receptor mediates the vascular relaxing effect of histamine and leads to an increase in heart rate.

Pharmacology

Antagonists of the H2 - receptor H2 antihistamines, have an important role in the therapy of gastric acid -related diseases, such as gastric and duodenal ulcers, although they have lost their role with respect to the proton pump inhibitors. The H2 antihistamines include, for example, cimetidine, ranitidine, famotidine and roxatidine.

Furthermore, H2 antihistamines (especially cimetidine and ranitidine, which are available to intravenous administration ) is used in combination with H1 - antihistamines in acute therapy of allergic shock and for the prophylaxis of anaphylactoid reactions.

H2 - receptor agonists, such Betazol other hand, have no therapeutic significance. You can, however, be used as diagnostics.