There are at least four known

endothelin Endothelins are peptides with receptors and effects in many body organs. Endothelin constricts blood vessels and raises blood pressure. The endothelins are normally kept in balance by other mechanisms, but when overexpressed, they contribute ...

receptors, ET_A, ET_B1, ET_B2 and ET_C, all of which are

G protein-coupled receptor G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily-related p ...

s whose activation result in elevation of intracellular-free

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...

, which constricts the smooth muscles of the blood vessels, raising blood pressure, or relaxes the smooth muscles of the blood vessels, lowering blood pressure, among other functions.

Physiological functions

*ET_A is a subtype for vasoconstriction These receptors are found in the smooth muscle tissue of

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

s, and binding of

to ET_A increases vasoconstriction (contraction of the blood vessel walls) and the retention of

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

, leading to increased blood pressure. *ET_B1 mediates vasodilation, When endothelin binds to ET_B1 receptors, this leads to the release of nitric oxide (also called

endothelium-derived relaxing factor Endothelium-derived relaxing factor (EDRF) is a name for a substance that Robert F. Furchgott discovered had the eponymous properties. Today, it is firmly established this substance is nitric oxide (NO). Endothelium produces NO which then diffu ...

natriuresis Natriuresis is the process of sodium excretion in the urine through the action of the kidneys. It is promoted by ventricular and atrial natriuretic peptides as well as calcitonin, and inhibited by chemicals such as aldosterone. Natriuresis lowers t ...

and diuresis (the production and elimination of urine) and mechanisms that lower blood pressure. *ET_B2 mediates vasoconstriction *ET_C has yet no clearly defined function. *ET receptors are also found in the nervous system where they may mediate

neurotransmission Neurotransmission (Latin: ''transmissio'' "passage, crossing" from ''transmittere'' "send, let through") is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron (the presynaptic neuron), ...

and vascular functions.

Brain and nerves

Widely distributed in the body, receptors for endothelin are present in blood vessels and cells of the brain,

choroid plexus The choroid plexus, or plica choroidea, is a plexus of cells that arises from the tela choroidea in each of the ventricles of the brain. Regions of the choroid plexus produce and secrete most of the cerebrospinal fluid (CSF) of the central nerv ...

and peripheral

nerves A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

. When applied directly to the brain of rats in picomolar quantities as an experimental model of stroke, endothelin-1 caused severe metabolic stimulation and

seizures An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with l ...

with substantial decreases in blood flow to the same brain regions, both effects mediated by calcium channels. A similar strong vasoconstrictor action of endothelin-1 was demonstrated in a

peripheral neuropathy Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or or ...

model in rats.

Clinical significance

Mutations in the EDNRB gene are associated with ABCD syndrome and some forms of

Waardenburg syndrome Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or one blue eye and one brown eye), a white foreloc ...

References

External links

* * G protein-coupled receptors {{transmembranereceptor-stub

Physiological functions

Brain and nerves

Clinical significance

See also

References

Further reading

External links