Angiotensin is a
peptide hormone
Peptide hormones or protein hormones are hormones whose molecules are peptide, or proteins, respectively. The latter have longer amino acid chain lengths than the former. These hormones have an effect on the endocrine system of animals, including h ...
that causes
vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessel ...
and an increase in
blood pressure
Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...
. It is part of the
renin–angiotensin system
The renin–angiotensin system (RAS), or renin–angiotensin–aldosterone system (RAAS), is a hormone system that regulates blood pressure, fluid and electrolyte balance, and systemic vascular resistance.
When renal blood flow is reduced, juxt ...
, which regulates blood pressure. Angiotensin also stimulates the release of
aldosterone
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a c ...
from the
adrenal cortex
The adrenal cortex is the outer region and also the largest part of an adrenal gland. It is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing specific hormones. It is ...
to promote sodium retention by the kidneys.
An
oligopeptide
An oligopeptide, often just called peptide ('' oligo-'', "a few"), consists of two to twenty amino acids and can include dipeptides, tripeptides, tetrapeptides, and pentapeptides. Some of the major classes of naturally occurring oligopeptides incl ...
, angiotensin is a
hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
and a
dipsogen A dipsogen is an agent that causes thirst. (From Greek language, Greek: ''δίψα'' ''(dipsa)'', "thirst" and the suffix ''-gen'', "to create".)
Physiology
Angiotensin II is thought to be a powerful dipsogen, and is one of the products of the reni ...
. It is derived from the precursor molecule angiotensinogen, a serum globulin produced in the
liver
The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...
. Angiotensin was isolated in the late 1930s (first named 'angiotonin' or 'hypertensin') and subsequently characterized and synthesized by groups at the
Cleveland Clinic
Cleveland Clinic is a nonprofit American academic medical center based in Cleveland, Ohio. Owned and operated by the Cleveland Clinic Foundation, an Ohio nonprofit corporation established in 1921, it runs a 170-acre (69 ha) campus in Cleveland, ...
and
Ciba laboratories.
Precursor and types
Angiotensinogen
![Angiotensinogen](https://upload.wikimedia.org/wikipedia/commons/1/16/Angiotensinogen.jpg)
Angiotensinogen is an
α-2-globulin synthesized in the liver and is a precursor for angiotensin, but has also been indicated as having many other roles not related to angiotensin peptides.
It is a member of the
serpin
Serpins are a Protein superfamily, superfamily of proteins with similar structures that were first identified for their Protease inhibitor (biology), protease inhibition activity and are found in all kingdom (biology), kingdoms of life. The acr ...
family of proteins, leading to another name: Serpin A8, although it is not known to inhibit other enzymes like most serpins. In addition, a generalized crystal structure can be estimated by examining other proteins of the serpin family, but angiotensinogen has an elongated
N-terminus
The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the ami ...
compared to other serpin family proteins.
Obtaining actual crystals for X-ray diffractometric analysis is difficult in part due to the variability of glycosylation that Angiotensinogen exhibits. The non-glycosylated and fully glycosylated states of angiotensinogen also vary in molecular weight, the former weighing 53kDa and the latter weighing 75kDa, with a plethora of partially glycosylated states weighing in between these two values.
Angiotensinogen is also known as
renin
Renin (etymology and pronunciation), also known as an angiotensinogenase, is an aspartic protease protein and enzyme secreted by the kidneys that participates in the body's renin–angiotensin–aldosterone system (RAAS)—also known as the r ...
substrate. It is cleaved at the N-terminus by renin to result in angiotensin I, which will later be modified to become angiotensin II.
This peptide is 485 amino acids long, and 10 N-terminus amino acids are cleaved when renin acts on it.
The first 12 amino acids are the most important for activity.
: Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-...
Plasma angiotensinogen levels are increased by plasma
corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involv ...
,
estrogen
Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal acti ...
,
thyroid
The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...
hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
, and angiotensin II levels. In mice with a full body deficit of angiotensinogen, the effects observed were low newborn survival rate, stunted body weight gain, stunted growth, and abnormal renal development.
Angiotensin I
:Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu , Val-Ile-...
Angiotensin I (
CAS# 11128-99-7), officially called proangiotensin, is formed by the action of
renin
Renin (etymology and pronunciation), also known as an angiotensinogenase, is an aspartic protease protein and enzyme secreted by the kidneys that participates in the body's renin–angiotensin–aldosterone system (RAAS)—also known as the r ...
on
angiotensinogen
Angiotensin is a peptide hormone that causes vasoconstriction and an increase in blood pressure. It is part of the renin–angiotensin system, which regulates blood pressure. Angiotensin also stimulates the release of aldosterone from the adren ...
. Renin cleaves the
peptide bond
In organic chemistry, a peptide bond is an amide type of covalent chemical bond linking two consecutive alpha-amino acids from C1 (carbon number one) of one alpha-amino acid and N2 (nitrogen number two) of another, along a peptide or protein cha ...
between the
leucine
Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α- ca ...
(Leu) and
valine
Valine (symbol Val or V) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α- carboxylic acid group (which is in the deprotonat ...
(Val) residues on angiotensinogen, creating the
decapeptide
Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides.
A p ...
(ten amino acid) (des-Asp) angiotensin I. Renin is produced in the
kidney
The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...
s in response to renal sympathetic activity, decreased intrarenal blood pressure (<90mmHg systolic blood pressure ) at the
juxtaglomerular cell
Juxtaglomerular cells (JG cells), also known as juxtaglomerular granular cells are cells in the kidney that synthesize, store, and secrete the enzyme renin. They are specialized smooth muscle cells mainly in the walls of the afferent arteriol ...
s, dehydration or decreased delivery of Na+ and Cl- to the
macula densa
In the kidney, the macula densa is an area of closely packed specialized cells lining the wall of the distal tubule, at the point where the thick ascending limb of the Loop of Henle meets the distal convoluted tubule. The macula densa is the t ...
.
If a reduced NaCl concentration in the distal tubule is sensed by the macula densa, renin release by juxtaglomerular cells is increased. This sensing mechanism for macula densa-mediated renin secretion appears to have a specific dependency on chloride ions rather than sodium ions. Studies using isolated preparations of
thick ascending limb
Within the nephron of the kidney, the ascending limb of the loop of Henle is a segment of the heterogenous loop of Henle downstream of the descending limb, after the sharp bend of the loop. This part of the renal tubule is divided into a thin and ...
with
glomerulus
''Glomerulus'' () is a common term used in anatomy to describe globular structures of entwined vessels, fibers, or neurons. ''Glomerulus'' is the diminutive of the Latin ''glomus'', meaning "ball of yarn".
''Glomerulus'' may refer to:
* the filter ...
attached in low NaCl perfusate were unable to inhibit renin secretion when various sodium salts were added but could inhibit renin secretion with the addition of
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
salts.
This, and similar findings obtained in vivo,
has led some to believe that perhaps "the initiating signal for MD control of renin secretion is a change in the rate of NaCl uptake predominantly via a luminal
Na,K,2Cl co-transporter whose physiological activity is determined by a change in luminal Cl concentration."
Angiotensin I appears to have no direct biological activity and exists solely as a precursor to angiotensin II.
Angiotensin II
:Asp-Arg-Val-Tyr-Ile-His-Pro-Phe
Angiotensin I is converted to angiotensin II (AII) through removal of two C-terminal residues by the enzyme ''
angiotensin-converting enzyme
Angiotensin-converting enzyme (), or ACE, is a central component of the renin–angiotensin system (RAS), which controls blood pressure by regulating the volume of fluids in the body. It converts the hormone angiotensin I to the active vasoconstr ...
'' (ACE), primarily through ACE within the lung (but also present in
endothelial cells
The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
, kidney epithelial cells, and the brain). Angiotensin II acts on the
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
to increase
vasopressin
Human vasopressin, also called antidiuretic hormone (ADH), arginine vasopressin (AVP) or argipressin, is a hormone synthesized from the AVP gene as a peptide prohormone in neurons in the hypothalamus, and is converted to AVP. It then travel ...
production, and also acts on venous and arterial smooth muscle to cause vasoconstriction. Angiotensin II also increases
aldosterone
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a c ...
secretion; it therefore acts as an
endocrine
The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neu ...
,
autocrine Autocrine signaling is a form of cell signaling in which a cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on that same cell, leading to changes in the cell. This can be contrasted with pa ...
/
paracrine Paracrine signaling is a form of cell signaling, a type of cellular communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells. Signaling molecules known as paracrine factors diffuse ove ...
, and
intracrine
Intracrine refers to a hormone that acts inside a cell, regulating intracellular events. In simple terms it means that the cell stimulates itself by cellular production of a factor that acts within the cell. Steroid hormones act through intracellu ...
hormone.
ACE is a target of
ACE inhibitor
Angiotensin-converting-enzyme inhibitors (ACE inhibitors) are a class of medication used primarily for the treatment of hypertension, high blood pressure and heart failure. They work by causing relaxation of blood vessels as well as a decrease i ...
drugs, which decrease the rate of angiotensin II production. Angiotensin II increases blood pressure by stimulating the Gq protein in vascular smooth muscle cells (which in turn activates an IP3-dependent mechanism leading to a rise in intracellular calcium levels and ultimately causing contraction). In addition, angiotensin II acts at the
Na+/H+ exchanger in the
proximal tubule
The proximal tubule is the segment of the nephron in kidneys which begins from the renal pole of the Bowman's capsule to the beginning of loop of Henle. It can be further classified into the proximal convoluted tubule (PCT) and the proximal straig ...
s of the kidney to stimulate Na
+ reabsorption and H
+ excretion which is coupled to bicarbonate reabsorption. This ultimately results in an increase in blood volume, pressure, and pH. Hence,
ACE inhibitor
Angiotensin-converting-enzyme inhibitors (ACE inhibitors) are a class of medication used primarily for the treatment of hypertension, high blood pressure and heart failure. They work by causing relaxation of blood vessels as well as a decrease i ...
s are major anti-hypertensive drugs.
Other cleavage products of ACE, seven or nine amino acids long, are also known; they have differential affinity for
angiotensin receptors, although their exact role is still unclear. The action of AII itself is targeted by
angiotensin II receptor antagonist
Angiotensin II receptor blockers (ARBs), formally angiotensin II receptor type 1 (AT1) antagonists, also known as angiotensin receptor blockers, angiotensin II receptor antagonists, or AT1 receptor antagonists, are a group of pharmaceuticals tha ...
s, which directly block
angiotensin II AT1 receptors.
Angiotensin II is degraded to angiotensin III by angiotensinases located in red blood cells and the vascular beds of most tissues. It has a half-life in circulation of around 30 seconds, whereas, in tissue, it may be as long as 15–30 minutes.
Angiotensin II results in increased
inotropy
An inotrope is an agent that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the force of muscular contractions. Positively inotropic agents increase the strength of muscular contraction.
The term ''inotr ...
,
chronotropy
Chronotropic effects (from ''chrono-'', meaning time, and ''tropos'', "a turn") are those that change the heart rate.
Chronotropic drugs may change the heart rate and rhythm by affecting the electrical conduction system of the heart and the ne ...
,
catecholamine
A catecholamine (; abbreviated CA) is a monoamine neurotransmitter, an organic compound that has a catechol (benzene with two hydroxyl side groups next to each other) and a side-chain amine.
Catechol can be either a free molecule or a subst ...
(
norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad'', ...
) release, catecholamine sensitivity, aldosterone levels, vasopressin levels, and cardiac remodeling and vasoconstriction through AT
1 receptors on peripheral vessels (conversely, AT
2 receptors impair cardiac remodeling). This is why ACE inhibitors and ARBs help to prevent remodeling that occurs secondary to angiotensin II and are beneficial in
congestive heart failure
Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...
.
Angiotensin III
:Asp , Arg-Val-Tyr-Ile-His-Pro-Phe
Angiotensin III has 40% of the
pressor
An antihypotensive agent, also known as a vasopressor agent or simply vasopressor, or pressor, is any substance, whether endogenous or a medication, that tends to raise low blood pressure. Some antihypotensive drugs act as vasoconstrictors to inc ...
activity of angiotensin II, but 100% of the aldosterone-producing activity. Increases
mean arterial pressure
In medicine, the mean arterial pressure (MAP) is an average blood pressure in an individual during a single cardiac cycle. MAP is altered by cardiac output and systemic vascular resistance.
Testing
Mean arterial pressure can be measured direct ...
. It is a peptide that is formed by removing an amino acid from angiotensin II by aminopeptidase A.
Activation of the AT2 receptor by angiotensin III triggers
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 ...
, while AT2 activation via angiotensin II does not. This natriuretic response via angiotensin III occurs when the AT1 receptor is blocked.
Angiotensin IV
:Arg , Val-Tyr-Ile-His-Pro-Phe
Angiotensin IV is a hexapeptide that, like angiotensin III, has some lesser activity. Angiotensin IV has a wide range of activities in the central nervous system.
The exact identity of AT4 receptors has not been established. There is evidence that the AT4 receptor is
insulin-regulated aminopeptidase (IRAP). There is also evidence that angiotensin IV interacts with the HGF system through the c-Met receptor.
Synthetic
small molecule
Within the fields of molecular biology and pharmacology, a small molecule or micromolecule is a low molecular weight (≤ 1000 daltons) organic compound that may regulate a biological process, with a size on the order of 1 nm. Many drugs ar ...
analogues of angiotensin IV with the ability to penetrate through
blood brain barrier
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the Cell (biology), cells, and transports Metabolic waste, metabolic waste products away from th ...
have been developed.
The AT4 site may be involved in memory acquisition and recall, as well as blood flow regulation.
Angiotensin IV and its analogs may also benefit spatial memory tasks such as object recognition and avoidance (conditioned and passive avoidance).
Studies have also shown that the usual biological effects of angiotensin IV on the body are not affected by common AT2 receptor antagonists such as the hypertension medication
Losartan
Losartan, sold under the brand name Cozaar among others, is a medication used to treat high blood pressure (hypertension). It is in the angiotensin II receptor antagonist, angiotensin receptor blocker (ARB) family of medication, and is consider ...
.
Effects
:''See also
Renin–angiotensin system#Effects''
Angiotensins II, III and IV have a number of effects throughout the body:
Adipic
Angiotensins "modulate fat mass expansion through upregulation of adipose tissue lipogenesis ... and downregulation of lipolysis."
Cardiovascular
Angiotensins are potent direct
vasoconstrictor
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessel ...
s, constricting arteries and veins and increasing blood pressure. This effect is achieved through activation of the
GPCR AT1, which signals through a
Gq protein
Gq protein alpha subunit is a family of heterotrimeric G protein alpha subunits. This family is also commonly called the Gq/11 (Gq/G11) family or Gq/11/14/15 family to include closely related family members. G alpha subunits may be referred ...
to activate phospholipase C, and subsequently increase intracellular calcium.
Angiotensin II has prothrombotic potential through adhesion and aggregation of
platelets
Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby ini ...
and stimulation of
PAI-1
Plasminogen activator inhibitor-1 (PAI-1) also known as endothelial plasminogen activator inhibitor or serpin E1 is a protein that in humans is encoded by the ''SERPINE1'' gene. Elevated PAI-1 is a risk factor for thrombosis and atherosclerosis
P ...
and
PAI-2.
When cardiac cell growth is stimulated, a local (autocrine-paracrine) renin–angiotensin system is activated in the cardiac myocyte, which stimulates cardiac cell growth through protein kinase C. The same system can be activated in smooth muscle cells in conditions of hypertension, atherosclerosis, or endothelial damage. Angiotensin II is the most important Gq stimulator of the heart during hypertrophy, compared to endothelin-1 and α1 adrenoreceptors.
Neural
Angiotensin II increases
thirst
Thirst is the craving for potable fluids, resulting in the basic instinct of animals to drink. It is an essential mechanism involved in fluid balance. It arises from a lack of fluids or an increase in the concentration of certain osmolites, suc ...
sensation (
dipsogen A dipsogen is an agent that causes thirst. (From Greek language, Greek: ''δίψα'' ''(dipsa)'', "thirst" and the suffix ''-gen'', "to create".)
Physiology
Angiotensin II is thought to be a powerful dipsogen, and is one of the products of the reni ...
) through the
area postrema
The area postrema, a paired structure in the medulla oblongata of the brainstem, is a circumventricular organ having permeable capillaries and sensory neurons that enable its dual role to detect circulating chemical messengers in the blood and ...
and
subfornical organ
The subfornical organ (SFO) is one of the circumventricular organs of the brain. Its name comes from its location on the ventral surface of the fornix near the interventricular foramina (foramina of Monro), which interconnect the lateral ventr ...
of the brain,
decreases the response of the
baroreceptor reflex
The baroreflex or
baroreceptor reflex is one of the body's homeostatic mechanisms that helps to maintain blood pressure at nearly constant levels. The baroreflex provides a rapid negative feedback loop in which an elevated blood pressure causes the ...
, increases the desire for
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...
, increases secretion of
ADH from the
posterior pituitary
The posterior pituitary (or neurohypophysis) is the posterior lobe of the pituitary gland which is part of the endocrine system. The posterior pituitary is not glandular as is the anterior pituitary. Instead, it is largely a collection of axonal ...
, and increases secretion of
ACTH
Adrenocorticotropic hormone (ACTH; also adrenocorticotropin, corticotropin) is a polypeptide tropic hormone produced by and secreted by the anterior pituitary gland. It is also used as a medication and diagnostic agent. ACTH is an important co ...
from the
anterior pituitary
A major organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular, anterior lobe that together with the posterior lobe (posterior pituitary, or the neurohypophysis) makes up the p ...
.
[ It also potentiates the release of ]norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad'', ...
by direct action on postganglionic sympathetic fibers.
Adrenal
Angiotensin II acts on the adrenal cortex
The adrenal cortex is the outer region and also the largest part of an adrenal gland. It is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing specific hormones. It is ...
, causing it to release aldosterone
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a c ...
, a hormone that causes the kidneys to retain sodium and lose potassium. Elevated plasma angiotensin II levels are responsible for the elevated aldosterone levels present during the luteal phase of the menstrual cycle
The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that make pregnancy possible. The ovarian cycle controls the production and release of eggs a ...
.
Renal
Angiotensin II has a direct effect on the proximal tubules to increase Na+ reabsorption
In renal physiology, reabsorption or tubular reabsorption is the process by which the nephron removes water and solutes from the tubular fluid (pre-urine) and returns them to the circulating blood. It is called ''reabsorption'' (and not ''absorpt ...
. It has a complex and variable effect on glomerular filtration
Renal functions include maintaining an acid–base balance; regulating fluid balance; regulating sodium, potassium, and other electrolytes; clearing toxins; absorption of glucose, amino acids, and other small molecules; regulation of blood pre ...
and renal blood flow
In the physiology of the kidney, renal blood flow (RBF) is the volume of blood delivered to the kidneys per unit time. In humans, the kidneys together receive roughly 25% of cardiac output, amounting to 1.2 - 1.3 L/min in a 70-kg adult male.
It ...
depending on the setting. Increases in systemic blood pressure will maintain renal perfusion pressure; however, constriction of the afferent and efferent glomerular arterioles will tend to restrict renal blood flow. The effect on the efferent arteriolar resistance is, however, markedly greater, in part due to its smaller basal diameter; this tends to increase glomerular capillary hydrostatic pressure and maintain glomerular filtration rate
Renal functions include maintaining an acid–base balance; regulating fluid balance; regulating sodium, potassium, and other electrolytes; clearing toxins; absorption of glucose, amino acids, and other small molecules; regulation of blood p ...
. A number of other mechanisms can affect renal blood flow and GFR. High concentrations of Angiotensin II can constrict the glomerular mesangium, reducing the area for glomerular filtration. Angiotensin II is a sensitizer to tubuloglomerular feedback In the physiology of the kidney, tubuloglomerular feedback (TGF) is a feedback system inside the kidneys. Within each nephron, information from the renal tubules (a downstream area of the tubular fluid) is signaled to the glomerulus (an upstream ar ...
, preventing an excessive rise in GFR. Angiotensin II causes the local release of prostaglandins, which, in turn, antagonize renal vasoconstriction. The net effect of these competing mechanisms on glomerular filtration will vary with the physiological and pharmacological environment.
See also
* ACE inhibitor
Angiotensin-converting-enzyme inhibitors (ACE inhibitors) are a class of medication used primarily for the treatment of hypertension, high blood pressure and heart failure. They work by causing relaxation of blood vessels as well as a decrease i ...
* Angiotensin receptor
The angiotensin II receptors, (ATR1) and (ATR2), are a class of G protein-coupled receptors with angiotensin II as their ligands. They are important in the renin–angiotensin system: they are responsible for the signal transduction of the vaso ...
* Angiotensin II receptor antagonist
Angiotensin II receptor blockers (ARBs), formally angiotensin II receptor type 1 (AT1) antagonists, also known as angiotensin receptor blockers, angiotensin II receptor antagonists, or AT1 receptor antagonists, are a group of pharmaceuticals tha ...
* Captopril
Captopril, sold under the brand name Capoten among others, is an ACE inhibitor, angiotensin-converting enzyme (ACE) inhibitor used for the treatment of hypertension and some types of congestive heart failure. Captopril was the first oral ACE inh ...
* Perindopril
Perindopril is a medication used to treat high blood pressure, heart failure, or stable coronary artery disease.
As a long-acting ACE inhibitor, it works by relaxing blood vessels and decreasing blood volume. As a prodrug, perindopril is ...
* Renin inhibitor
Renin inhibitors are pharmaceutical drugs inhibiting the activity of renin that is responsible for hydrolyzing angiotensinogen to angiotensin I, which in turn reduces the formation of angiotensin II that facilitates blood pressure.
Renin inhibit ...
References
Further reading
*
* ''Brenner & Rector's The Kidney'', 7th ed., Saunders, 2004.
* ''Mosby's Medical Dictionary'', 3rd Ed., CV Mosby Company, 1990.
* ''Review of Medical Physiology'', 20th Ed., William F. Ganong, McGraw-Hill, 2001.
* ''Clinical Physiology of Acid-Base and Electrolyte Disorders'', 5th ed., Burton David Rose & Theodore W. Post McGraw-Hill, 2001
*
*
*
*
*
*
*
External links
* The MEROPS
MEROPS is an online database for peptidases (also known as proteases, proteinases and proteolytic enzymes) and their inhibitors. The classification scheme for peptidases was published by Rawlings & Barrett in 1993, and that for protein inhibitor ...
online database for peptidases and their inhibitors
I04.953
*
*
*
{{Authority control
Peptide hormones
Angiology
Endocrinology
Hypertension
Hexapeptides