Stimulus for ANP Release

Atrial natriuretic peptide (ANP) is a hormone produced by atria of heart mainly in response to-

Correct Answer: Increased blood volume

Atrial Natriuretic Peptide (ANP) is secreted by the cardiac atria (mainly right atrium) in response to increased blood volume (stretch of atrial walls). It acts to reduce blood pressure and volume.

Actions of ANP

• Increases renal Na⁺ secretion (natriuresis) → water follows → reduced blood volume
• Increases K⁺ reabsorption
• Inhibits renin, aldosterone, and ADH release → reduces Na⁺ and water retention
• Causes vasodilation → reduces blood pressure

ANP vs. Aldosterone — Antagonistic Pair

• Aldosterone (adrenal cortex) → Na⁺ reabsorption → ↑ blood volume and pressure
• ANP (heart atria) → Na⁺ secretion → ↓ blood volume and pressure

ANP vs. ADH

• ADH (Vasopressin): released in response to hyperosmolarity of blood or hypovolemia → water reabsorption → ↑ blood volume
• ANP: released in response to hypervolemia → opposes ADH and aldosterone

Memory Tip

ANP = Atrial Natriuretic Peptide → secreted when atria are stretched by too much blood → tells kidney to excrete Na⁺ and water to relieve the stretch.