Renal & Adrenal Endocrinology — Angiotensin

Angiotensinogen is a peptide hormone produced by the liver

1. Angiotensin 1 (decapeptide)
   • ↑ Renin by JGA → cleavage of Angiotensinogen → AT1
   • No biological activity
2. Angiotensin 2 (octapeptided)
   • ACE in pulmonary capil endothelia
   • → ↑AT2
3. Angiotensin 3 (septapeptide)
   • 40% of the pressor activity AT2
   • 100% of the aldosterone-producing activity
4. Angiotensin 4 (hexapeptide)
   • Minimal biological activity

Actions of AT2 include:

• Acts via GPCR (Gq via PLC to increase IP3 and intracellular Ca)
• CVS
  • Vasopressor
  • Resets baroreceptor control of HR at higher pressure
  • Potent mitogen for smooth muscle and cardiac myocytes
  • Direct positive inotrope
• CNS
  • ↑ sympathetic outflow
  • ↑ thirst
  • ↑ ADH release from posterior pituitary.
• Renal
  • Negative feedback on renin release
  • ↑ aldosterone release
  • ↓ RBF and GFR
  • Direct renal arteriole constriction (efferent = afferent)
  • Mesangial cell contraction thus ↓ Kf and GFR
  • ↑ sodium/chloride reabsorption in PCT
  • Direct effect and via ↑ aldosterone release

Factors which alter renin release cause a corresponding change in Angiotensin 2

• Stimulation of renin secretion (↑ renin → ↑ angiotensin 2)
  • β-1 agonism
  • ↓ renal perfusion pressure
  • ↓ sodium delivery to DCT
  • Prostaglandins
• Inhibition or renin secretion (↓ renin → ↓ angiotensin 2):
  • ↑ renal perfusion pressure (via afferent arteriolar dilatation)
  • ↑ sodium delivery to DCT
  • ↑ by angiotensin II (negative feedback) and vasopressin

Gladwin 2016

Answer by Gladwin