1. Atrial Natriuretic Peptides [ANP]
20/01/2012

2. Atrial Natriuretic Peptides
Atrial natriuretic peptide (ANP), atrial natriuretic factor (ANF), atrial natriuretic hormone (ANH), or atriopeptin, is a powerful vasodilator, and a protein (polypeptide) hormone secreted by heart muscle cells.
It is involved in the homeostatic control of body water, sodium, potassium and fat (adipose tissue).
It is released by muscle cells in the upper chambers (atria) of the heart (atrial myocytes) in response to high blood pressure.
ANP acts to reduce the water, sodium and adipose loads on the circulatory system, thereby reducing blood pressure.1
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3. Learning Objectives Nature and biosynthesis Main effects
Mechanism of action
Therapeutic potential
31/12/2018

4. Atrial Natriuretic Peptides – 1) Nature and Biosynthesis
Atrial cells have a specialised endocrine function in relation to the cardiovascular system
They contain secretory granules, and store and release atrial natriuretic peptides (ANP) with powerful effects on the kidney and vascular system
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5. Two related natriuretic peptides (B and C) are found
Release of ANP occurs during volume overload in response to stretching of the atria
Two related natriuretic peptides (B and C) are found
BNP is found in ventricular muscle
CNP is found in vascular endothelium
The plasma concentration of B-type natriuretic Peptide (BNP) is predictably increased in patients with heart failure and is increasingly used as an aid to diagnosis
31/12/2018

6. Atrial Natriuretic Peptides – 2) Main Effects
To increase Na+ and water excretion by the kidney
Relax vascular smooth muscle (except efferent arterioles of renal glomeruli)
Increase vascular permeability
Inhibit the release and/or actions of several hormones and mediators including aldosterone, angiotensin II, endothelin and antidiuretic hormone (ADH)
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7. Atrial Natriuretic Peptides – 3) Mechanism of Action
ANPs exert their action by combining with membrane receptors (natriuretic peptide receptors, NPRs) which exist at least in two subtypes (A and B)
Both NPR-A and NPR-B incorporate a catalytic guanylate cyclase moiety
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8. Atrial Natriuretic Peptides – Mechanism of Action
ANP-receptor binding leads to increase cGMP (cyclic 3’5’-guanosine monophosphate) intracellular generation, same response as that produced by organic nitrates and endothelial-derived-NO (nitric oxide)
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9. Elsewhere ANP cause vasodilatation and reduce blood pressure
However, interaction is through membrane-bound guanylate cyclase for ANP and soluble guanylate cyclase for organic nitrates and endothelial NO
Renal glomerular arterioles are dilated by ANP but efferent arterioles are constricted increasing filtration pressure leading to increased glomerular filtration and enhanced Na+ excretion
Elsewhere ANP cause vasodilatation and reduce blood pressure
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10. Atrial Natriuretic peptides – 4) Therapeutic Potential
Vasodilations leads to decreased cardiac load (pre- and afterload)
Increase Na+ and water excretion leads to reduction in preload
For example: Nesiritide, a recombinant form of human B-type natriuretic peptide (BNP) approved by the FDA for the treatment of acute heart failure syndromes
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11. However, a pooled analysis of randomised controlled trials has suggested that it too may increase mortality
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