science

Vasopressin receptor antagonist

Vasopressin receptor antagonist is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Vasopressin receptor antagonist rather than just read about it. In short: A vasopressin receptor antagonist (VRA) is an agent that interferes with action at the vasopressin receptors. Most commonly VRAs are used in the treatment of hyponatremia, especially in patients with congestive heart failure, liver cirrhosis or SIADH.

Key takeaways

Vasopressin receptor antagonist belongs to science; place it in that map before memorising details.
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Reproduce the core statement of Vasopressin receptor antagonist from memory before moving on to harder problems.

Reference excerpt

A vasopressin receptor antagonist (VRA) is an agent that interferes with action at the vasopressin receptors. Most commonly VRAs are used in the treatment of hyponatremia, especially in patients with congestive heart failure, liver cirrhosis or SIADH.

Types

Vaptans The "vaptan" drugs act by directly blocking the action of vasopressin at its receptors (V1A, V1B and V2). These receptors have a variety of functions, with the V1A and V2 receptors are expressed peripherally and involved in the modulation of blood pressure and kidney function respectively, while the V1A and V1B receptors are expressed in the central nervous system. V1A is expressed in many regions of the brain, and has been linked to a variety of social behaviors in humans and animals. The vaptan class of drugs contains a number of compounds with varying selectivity, several of which are either already in clinical use or in clinical trials as of 2009.

Unselective (mixed V1A/V2) Conivaptan V1A selective (V1RA) Relcovaptan V1B selective (V3RA) Nelivaptan V2 selective (V2RA) Lixivaptan Mozavaptan Satavaptan Tolvaptan

Somatostatin Somatostatin is a competitive inhibitor.

Demeclocycline and lithium Demeclocycline, a tetracycline antibiotic, is sometimes used to block the action of vasopressin in the kidney in hyponatremia due to inappropriately high secretion of vasopressin (SIADH), when fluid restriction has failed. Demeclocycline is not a direct antagonist of the vasopressin receptors however, but rather inhibits activation of the intracellular second messenger cascade of this receptor in the kidney by an unknown mechanism. Lithium, as lithium carbonate, possesses similar properties to those of demeclocycline on the action of vasopressin in the kidney, and was used clinically before demeclocycline, which largely superseded it for this indication.

Medical use

Hyponatremia V2R antagonists have become a mainstay of treatment for euvolemic (i.e., SIADH, postoperative hyponatremia) and hypervolemic hyponatremia (i.e., CHF and cirrhosis). V2RAs predictably cause aquaresis leading to increased [Na+] in majority of patients with hyponatremia due to SIADH, CHF, and cirrhosis. The optimum use of VRAs has not yet been determined, but some predictions can be made with reasonable certainty. For hyponatremia in hospitalized patients, who are unable to take medication orally or for those in whom a more rapid correction of hyponatremia is desired, conivaptan (V1/V2R antagonist) will likely be the preferred agent. Selective V2R antagonists such as tolvaptan or lixivaptan will likely be useful in patients for whom oral therapy is suitable and for more chronic forms of hyponatremia.

Congestive heart failure Neurohormonal activation characteristic of CHF, including increased renin, angiotensin, aldosterone, and catecholamines, contributes to progression of CHF. It has been suggested that cardiovascular mortality may be reduced by selective V2RA such as tolvaptan in the higher risk group with kidney function impairment or severe congestive findings. But until FDA indication is granted for use in CHF with or without accompanying hyponatremia, VRAs are not recommended in patients with CHF.

Cirrhosis V2RA may be particularly beneficial in the treatment of patients with advanced liver cirrhosis and ascites. Blockade of V2R will induce an effective aquaresis and inhibition of V2-mediated vasodilation. This aquaresis, in combination with a diuresis, may provide a potential therapy for patients with resistant ascites. V2 receptor antagonism increases plasma vasopressin concentration, which may cause unopposed hyperstimulation of the vasoconstrictor V1 receptor. Given the potential hyperstimulation of V1R, V2RA may have additional secondary preventative benefits in patients with cirrhosis through a reduction in portal pressure and a decreased risk of variceal bleeding.

Polycystic kidney disease Polycystin defects increase intracellular cAMP, secondary messenger for vasopressin acting at V2R, leading to cyst development. cAMP-dependent genes promote fluid secretion into developing renal cysts and increase cell proliferation. Studies in several animal models of polycystic kidney disease have shown a reduction in kidney size and cyst volume after treatment with specific V2 receptor antagonist. Full scale therapeutic trials of V2RAs in patients with autosomal dominant polycystic kidney disease are currently ongoing.

Nephrogenic diabetes insipidus Congenital nephrogenic diabetes insipidus (NDI) may result from V2R or aquaporin-2 (AQP2) mutations. Exogenously administered V2R antagonists can bind to misfolded intracellular V2R, and improve transport of V2R to the cell membrane. Clinical studies in patients with X-linked NDI showed that the selective V1R antagonist relcovaptan (SR49059, Sanofi-Aventis) significantly increased urine osmolality and decreased 24-hour urine flow. Thus V1R and/or V2R antagonists may serve as molecular chaperones to mitigate misfolding defects in selected patients with type 2 NDI.

References

Worked examples

Example 1 — a first encounter with Vasopressin receptor antagonist

Start with the simplest possible case. Write down what Vasopressin receptor antagonist claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Vasopressin receptor antagonist before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Vasopressin receptor antagonist ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Vasopressin receptor antagonist

In research: Vasopressin receptor antagonist appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Vasopressin receptor antagonist in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Vasopressin receptor antagonist is common in secondary-school and first-year university syllabi. It links to neighbouring topics Vasopressin receptor antagonists, World Anti-Doping Agency prohibited substances, so understanding it makes those chapters shorter.
In everyday life: Look for Vasopressin receptor antagonist outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Vasopressin receptor antagonist in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Vasopressin receptor antagonist means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
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Frequently asked questions

What is Vasopressin receptor antagonist in simple terms?

Why does Vasopressin receptor antagonist matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Vasopressin receptor antagonist?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Vasopressin receptor antagonist.