Question.

Angiotensin II has all the following physiological effects EXCEPT which one?
a. Increased thirst
b. Arteriolar vasoconstriction
c. Renin release from the juxtaglomerular apparatus
d. Suppression of aldosterone release from the adrenal cortex
e. Stimulation of anti-diuretic hormone (ADH) release from the posterior pituitary

 

 

 

Answer.

The answer is d. Angiotensin II stimulates aldosterone release.

Explanation.

Renin is released from the juxtaglomerular apparatus of the kidney in response to sympathetic nervous activity, falling renal tubular flow and, in particular, renal hypoperfusion.

Renin cleaves circulating angiotensinogen to angiotensin I. Angiotensin I is converted to angiotensin II by angiotensin converting enzyme (ACE) in the lungs. Angiotensin II acts on angiotensin receptors (AT1R & AT2R) to exert the following physiological effects:
• Promotes thirst and consequent water intake
• Increases sympathetic activity
• Arteriolar vasoconstriction (remember angio-tensing!)
• Stimulates aldosterone secretion from the adrenal cortex. Aldosterone is a mineralocorticoid which promotes sodium and water retention by the kidney.
• Stimulates the anterior pituitary to secrete more anti-diuretic hormone (ADH). ADH increases the permeability of the collecting dusts to water and thereby promotes renal water retention.

Overall, these actions are all designed to increase blood pressure and blood volume and thereby restore renal perfusion.

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