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Brain Natriuretic Peptide (BNP)
Related Subjects: |Water Physiology |Sodium Physiology |Potassium Physiology |Aldosterone Physiology |Atrial Natriuretic Peptide (ANP) |Brain Natriuretic Peptide (BNP)
🫀 Brain Natriuretic Peptide (BNP): Despite its name, BNP is produced mainly in the ventricles (not the brain). It is secreted in response to ↑ ventricular wall stretch and pressure overload, promoting natriuresis (Na⁺ excretion), diuresis 💧, vasodilation, and suppression of the RAAS. It is a cornerstone biomarker in Heart Failure.
🧬 Synthesis and Release
- Synthesis:
- Formed as pre-proBNP → cleaved to proBNP → split into active BNP + inactive NT-proBNP.
- Stimuli for release:
- ↑ Ventricular volume / pressure (e.g. HF).
- Cardiac stress or myocardial stretch.
- Neurohormonal triggers: endothelin, angiotensin II.
⚙️ Mechanism of Action
- BNP binds to NPR-A receptors → activates guanylyl cyclase → ↑ cGMP.
- cGMP mediates vasodilation, natriuresis, diuresis, and RAAS inhibition.
📊 Physiological Effects
- Natriuresis & Diuresis 💧: ↑ renal Na⁺ + water excretion → ↓ preload & blood volume.
- Vasodilation 🫀: ↓ systemic vascular resistance → ↓ afterload & BP.
- RAAS suppression: ↓ renin & aldosterone secretion → reduced Na⁺ retention.
- ↓ Sympathetic tone: Inhibits norepinephrine release → ↓ HR & BP.
- Anti-remodelling: Anti-fibrotic & anti-hypertrophic effects on myocardium.
🩺 Clinical Relevance
- Diagnosis & Monitoring of Heart Failure:
- BNP / NT-proBNP widely used biomarkers.
- High levels = ↑ cardiac wall stress, worse prognosis.
- Serial levels can guide therapy.
- Therapeutics: Recombinant BNP (nesiritide) used in acute HF (promotes vasodilation & diuresis).
- Prognostic role: Elevated in ACS, pulmonary hypertension, hypertensive heart disease.
- Limitations: Levels influenced by age (↑), renal impairment (↑), and obesity (↓).
🔑 Exam Tip
- BNP is measured in clinical practice, not ANP. NT-proBNP is more stable and often preferred in lab testing.
📝 Summary
BNP is a key ventricular stretch hormone regulating fluid and BP homeostasis via natriuresis, diuresis, vasodilation, and RAAS inhibition. Its major clinical value is as a diagnostic and prognostic biomarker in heart failure, with NT-proBNP widely used in practice. Remember: "BNP = Bad News Peptide" when elevated 🫀.
📚 References
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