Makindo Medical Notes

Atrial Natriuretic Peptide (ANP): ANP is a peptide hormone that acts as a vasodilator, diuretic, and natriuretic agent. It suppresses both sympathetic tone and the renin-angiotensin-aldosterone system (RAAS), playing a critical role in fluid and blood pressure regulation.

About

• Source: Primarily secreted by myocytes of the right atrium and ventricle in response to increased blood volume or atrial stretch.
• Both atria contribute to ANP secretion (right atrium > left atrium).
• Structure: A 28-amino acid peptide hormone that exerts its effects via cyclic guanosine monophosphate (cGMP).
• Degradation: ANP is broken down by neutral endopeptidase enzymes.

Effects

• Renal Effects:
  • Increases glomerular filtration rate (GFR) by dilating afferent arterioles and constricting efferent arterioles.
  • Decreases sodium reabsorption by inhibiting sodium channels in the apical membrane of renal tubular cells.
  • Promotes diuresis and natriuresis, reducing circulating blood volume.
• Vascular Effects:
  • Powerful vasodilator, reducing systemic vascular resistance and blood pressure.
• Systemic Effects:
  • Suppresses sympathetic nervous system activity and the RAAS.
  • Involved in regulating body water, sodium, potassium, and adipose tissue levels.

Clinical Relevance

• Elevated Levels: ANP levels are increased in hypervolemic states, such as:
  • Heart failure.
  • Chronic kidney disease.
  • Liver cirrhosis with ascites.
• Diagnostic Marker: ANP can serve as a biomarker for fluid overload and heart failure severity.

Mechanism of Action

• ANP binds to natriuretic peptide receptors (NPR-A) on target cells, activating guanylate cyclase and increasing intracellular cGMP levels.
• cGMP mediates vasodilation, natriuresis, and diuresis by:
  • Relaxing vascular smooth muscle cells.
  • Inhibiting sodium reabsorption in the renal tubules.
  • Suppressing aldosterone secretion from the adrenal cortex.

Uses

• ANP analogs or related therapies are under investigation for treating conditions like:
  • Acute heart failure.
  • Hypertension.
  • Renal disorders with fluid overload.

References

• ANP Mechanisms - NCBI
• UpToDate: Atrial Natriuretic Peptide