H2 receptor
Encyclopedia
H2 receptors are positively coupled to adenylate cyclase
via Gs. It is a potent stimulant of cAMP production. It increases the intracellular Ca2+ concentrations and release Ca2+ from intracellular stores. The drug betazole
is an example of a Histamine
H2 receptor agonist.
is a ubiquitous messenger molecule released from mast cell
s, enterochromaffin-like cells, and neuron
s. Its various actions are mediated by histamine receptors H1, H2, H3 and H4. The histamine receptor H2 belongs to the rhodopsin
-like family of G protein-coupled receptor
s. It is an integral membrane protein
and stimulates gastric acid secretion. It also regulates gastrointestinal motility and intestinal secretion and is thought to be involved in regulating cell growth and differentiation.
Adenylate cyclase
Adenylate cyclase is part of the G protein signalling cascade, which transmits chemical signals from outside the cell across the membrane to the inside of the cell ....
via Gs. It is a potent stimulant of cAMP production. It increases the intracellular Ca2+ concentrations and release Ca2+ from intracellular stores. The drug betazole
Betazole
Betazole is a histamine H2 receptor agonist. Also known as Ametazole. Betazole hydrochloride is known as gastramine and histalog.It has been used as a gastric stimulant to test for maximal production of gastric secretion activity The test can be used in diagnosis of diseases such as...
is an example of a Histamine
Histamine
Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
H2 receptor agonist.
Function
HistamineHistamine
Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
is a ubiquitous messenger molecule released from mast cell
Mast cell
A mast cell is a resident cell of several types of tissues and contains many granules rich in histamine and heparin...
s, enterochromaffin-like cells, and neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
s. Its various actions are mediated by histamine receptors H1, H2, H3 and H4. The histamine receptor H2 belongs to the rhodopsin
Rhodopsin
Rhodopsin, also known as visual purple, is a biological pigment of the retina that is responsible for both the formation of the photoreceptor cells and the first events in the perception of light. Rhodopsins belong to the G-protein coupled receptor family and are extremely sensitive to light,...
-like family of G protein-coupled receptor
G protein-coupled receptor
G protein-coupled receptors , also known as seven-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors , comprise a large protein family of transmembrane receptors that sense molecules outside the cell and activate inside signal...
s. It is an integral membrane protein
Integral membrane protein
An integral membrane protein is a protein molecule that is permanently attached to the biological membrane. Proteins that cross the membrane are surrounded by "annular" lipids, which are defined as lipids that are in direct contact with a membrane protein...
and stimulates gastric acid secretion. It also regulates gastrointestinal motility and intestinal secretion and is thought to be involved in regulating cell growth and differentiation.
Tissue distribution
- Gastric parietal cells (oxyntic cells)
- Vascular smooth muscleVascular smooth muscleVascular smooth muscle refers to the particular type of smooth muscle found within, and composing the majority of the wall of blood vessels.Vascular smooth muscle contracts or relaxes to both change the volume of blood vessels and the local blood pressure, a mechanism that is responsible for the...
- Neutrophils
- Central nervous systemCentral nervous systemThe central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
- HeartHeartThe heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
- UterusUterusThe uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
Physiological responses
Activation of the H2 receptor results in the following physiological responses:- Stimulation of gastric acidGastric acidGastric acid is a digestive fluid, formed in the stomach. It has a pH of 1 to 2 and is composed of hydrochloric acid , and large quantities of potassium chloride and sodium chloride...
secretion (Target of anti-histaminergics for peptic ulcer disease) - Smooth muscleSmooth muscleSmooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...
relaxation (histaminergic antagonists used for peptic - Inhibit antibodyAntibodyAn antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
synthesis, T-cell proliferation and cytokineCytokineCytokines are small cell-signaling protein molecules that are secreted by the glial cells of the nervous system and by numerous cells of the immune system and are a category of signaling molecules used extensively in intercellular communication...
production - VasodilationVasodilationVasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...
– PKA activity causes phosphorylation of MLCP, increasing its activity, resulting in MLC of myosinMyosinMyosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility. The term was originally used to describe a group of similar...
being dephosphorylated and thus inhibiting contraction. The smooth muscle relaxation leads to vasodilation.