Atrial Natriuretic Peptide
ATRIAL NATRIURETIC PEPTIDE
Introduction:
- A type of peptide hormone causing natriuresis (Increased Na+ excretion)
- Present as granules in atrial muscle cells.
- Cyclic GMP act on Atrial natriuretic peptide
Regulation of secretion:
- Released in response to increased plasma Na+ concentration & raised BP.
MAJOR PHYSIOLOGICAL EFFECTS:
- Mainly acts on Kidney & Blood vessels
- Effects of ANP are physiologically antagonistic to angiotensin II
1. Causes natriuresis (Increased Na+ excretion) by
- Increasing GFR
- Relaxing mesangial cells of glomerulus
- Reducing Na+ reabsorption from distal tubule & collecting ducts.
2. Reduces secretion of renin, aldosterone & ADH.
- Inhibit ADH-stimulated water reabsorption across collecting ducts.
- By inhibiting synthesis of aldosterone in the adrenal cortex
3. Reduces BP by,
- Decreasing total peripheral resistance.
- Enhancing urinary excretion of NaCl & water.
- Increasing capillary permeability.
4. Powerful Vasodilator
- Relaxes vascular smooth muscle in arterioles & venules.
- Lowers BP.
Specific effects of ANP:
1. Role of ANP in delaying onset of cardiac compensation:
- Secretion increases on stretching of atrial walls.
Heart failure –
- Circulating ANP levels increases 5-10 folds
- Direct effect on kidney on NaCl & water hemostasis
- Prevents extreme congestive symptoms during cardiac failure.
2. Biomarker:
- Used as biomarkers for CVs diseases such as stroke, MI, coronary artery disease & heart failure.
Exam Question
ATRIAL NATRIURETIC PEPTIDE
- ANP causing natriuresis (Increased Na+ excretion), by increasing GFR & reducing Na+ reabsorption from distal tubule & collecting ducts.
- Cyclic GMP act on Atrial natriuretic peptide.
- Effects of ANP are physiologically antagonistic to angiotensin II, mainly acts on kidney & blood vessels.
- Reduces secretion of renin, aldosterone & ADH, inhibit ADH-stimulated water reabsorption across collecting ducts.
- ANP is “Powerful vasodilator” relaxes vascular smooth muscle in arterioles & venules, lowering BP.
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