Difference Between ANP and BNP

The key difference between ANP and BNP is that the main secretion site of ANP is the atria while the main secretion site of BNP is the ventricles.

Natriuretic peptides are peptide hormones secreted by the heart, brain and other organs. Atrial and ventricular distension and neurohumoral stimuli stimulate the secretion of natriuretic peptide hormones by the heart. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are two types of natriuretic peptides. The main function of natriuretic peptides is to reduce arterial pressure by decreasing blood volume and systemic vascular resistance. Moreover, they decrease central venous pressure, pulmonary capillary wedge pressure, and cardiac output. Both ANP and BNP are useful diagnostic markers for heart failure in patients. They are released in response to cardiac distension, sympathetic stimulation and angiotensin 2.

CONTENTS

1. Overview and Key Difference
2. What is ANP 
3. What is BNP
4. Similarities Between ANP and BNP
5. Side by Side Comparison – ANP vs BNP in Tabular Form
6. Summary

What is ANP?

The atrial natriuretic peptide is a peptide hormone synthesized and stored mainly by the atrial myocytes. It is a 28 amino acid peptide. ANPs are synthesized in response to atrial distension, angiotensin II stimulation, endothelin, and sympathetic stimulation. Therefore, the level of ANP increases during the elevated blood volume caused due to heart failure. Atrial myocytes synthesize prepro-ANP and then cleave to pro-ANP and finally to biologically active ANP.

What is BNP?

Brain natriuretic peptide or BNP is another peptide-protein secreted mainly by ventricles. The brain also produces BNP in small amounts. BNP is a 32 amino acid peptide. Similar to ANP synthesis, BNP is also first synthesized as prepro-BNP. Then it is cleaved to pro-BNP and then to BNP.

BNP produces selective afferent arteriolar vasodilation, inhibits sodium reabsorption in the proximal convoluted tubule and inhibits renin and aldosterone release. Compared to ANP, BNP has potentially important diagnostic, therapeutic, and prognostic implications.

What are the Similarities Between ANP and BNP?

• ANP and BNP are biological active peptide hormones.
• They are endogenously produced by cardiomyocytes of cardiac tissue as cardiac hormones.
• Plasma levels of ANP and BNP elevate in chronic heart failure.
• Both bind to natriuretic peptide receptor-A.
• Ventricles are important sites for both BNP and ANP.
• Myocardial stretch is a key factor in the stimulation of the secretion of ANP and BNP.
• Moreover, both show effects on vasodilation, natriuresis, and inhibition of the renin-angiotensin-aldosterone (RAA) and the sympathetic nervous systems.
• ANP and BNP also inhibit aldosterone production.
• Both are useful markers of the heart’s status during treatment for heart failure.
• Besides, their synthesis begins as prepro-ANP or BNP and then covert into pro-ANP or BNP and finally to ANP or BNP.
• BNP is released by the same mechanisms that release ANP, and it has similar physiological actions.

What is the Difference Between ANP and BNP?

ANP and BNP are cardiac hormones. ANP is mainly synthesized in and secreted from the cardiac atrium while BNP is predominantly secreted in the cardiac ventricle. So, this is the key difference between ANP and BNP. Structurally, ANP is composed of 28 amino acid peptide, while BNP is composed of 32 amino acid peptide. Moreover, ANP was isolated and identified first, and then BNP was identified. Furthermore, the weight of ANP is 3078 Da while the weight of BNP is 3462 Da.

The following table summarizes the difference between ANP and BNP.

Summary – ANP vs BNP

There are three types of natriuretic peptides as ANP, BNP and CNP. ANP and BNP are secreted by the heart and act as cardiac hormones. The site of secretion of ANP is atria while the site of BNP secretion is ventricles. Thus, this is the key difference between ANP and BNP. Moreover, ANP is a peptide composed of 28 amino acid sequence while BNP is a peptide composed of 32 amino acid sequence.

Reference:

1. “Atrial and Brain Natriuretic Peptides.” Image for Cardiovascular Physiology Concepts, Richard E Klabunde PhD, Available here.
2. Nakagawa, Yasuaki, et al. “Atrial and Brain Natriuretic Peptides: Hormones Secreted from the Heart.”Peptides, Elsevier, 31 May 2018, Available here.

Image Courtesy:

1. “ANP-structure” Von Die Autorenschaft wurde nicht in einer maschinell lesbaren Form angegeben. Es wird Iridos als Autor angenommen (basierend auf den Rechteinhaber-Angaben). – Die Autorenschaft wurde nicht in einer maschinell lesbaren Form angegeben. Es wird angenommen, dass es sich um ein eigenes Werk handelt (basierend auf den Rechteinhaber-Angaben) (Gemeinfrei) via Commons Wikimedia
2. “BNP funcional” By BotanyBRA – Criação própria com o software Photoshop CS3 baseado em (Public Domain) via Commons Wikimedia