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angiotensin

angiotensin

see also:

image courtesy of wikipedia

introduction

  • angiotensin II is a peptide hormone that produces vasoconstriction, promotes water and salt retention, increased BP, and stimulates release of aldosterone
  • circulating inactive angiotensinogen is a globulin produced by the liver and converted to inactive angiotensin I by renin
  • the inactive angiotensin I is then converted to active angiotensin II by angiotensin converting enzyme (ACE) mainly within the lung but also in endothelium and renal epithelium
  • angiotensin II has a half life in the circulation of ~30secs (may be up to 30 minutes in tissues) and is degraded by:
    • angiotensinases to angiotensin III which has 100% of aldosterone stimulating activity but only 40% of pressor activity
      • angiotensin III is degraded to angiotensin IV which is partly active
    • ACE2 to the vasodilator, angiotensin-(1-7)
  • angiotensins act on angiotensin receptors which are blocked by angiotensin receptor blockers

angiotensin receptors

AT1 receptor

  • main receptor acted on by AG II
  • causes vasoconstriction, aldosterone secretion, etc

AT2 receptor

  • probably involved in fetal vascular growth and other tissue growth
  • activated by AG II

AT3 receptor

  • poorly characterized as yet

AT4 receptor

  • poorly characterized as yet
  • activated by AG IV
  • may have roles in CNS extracellular matrix and in modulation of oxytocin release

actions of angiotensin II (Ang II)

  • constricts arteries and veins and increasing blood pressure
  • prothrombotic
    • stimulation of PAI-1 and PAI-2
    • increased adhesion and aggregation of platelets
  • Gq stimulator of the heart causing cardiac hypertrophy
  • increases thirst sensation and salt desire
  • directly increases renal sodium reabsorption
  • potentiates the release of noradrenaline / norepinephrine
  • decreases the response of the baroreceptor reflex
  • increases aldosterone secretion
  • complex effects on GFR and RBF
  • sensitizes to tubuloglomerular feedback
  • causes the local release of prostaglandins in kidney which antagonise renal vasoconstriction
  • upregulates of adipose tissue lipogenesis
  • downregulates lipolysis

Angiotensin-(1-7)

  • this vasodilator peptide generally appears to oppose the pressor, proliferative and pro-fibrotic actions of Ang II
  • acts through its own G-protein-coupled receptor
angiotensin.txt · Last modified: 2020/03/25 21:17 (external edit)