9. Aldosterone and the RAAS Flashcards Preview

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Flashcards in 9. Aldosterone and the RAAS Deck (10)
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1
Q

What type of hormones is aldosterone? Where is it released from?

A

mineralocorticoid

zona glomerulosa cells

2
Q

What effect does aldosterone have on BP?

A

Increases Na+ and water reabsorption in the kidneys… increases extracellular volume… increases arterial BP

3
Q

How does aldosterone increase BP?

A

Acts at nuclear mineralocorticoid receptors in distal tubules and collecting duct cells of kidney nephrons:

  1. upregulates expression of basolateral Na+/K+ pump… pumps 3 Na+ ions out of cell into interstitial fluid (and 2 K+ ions in)… promotes conc. gradient allowing Na+ and water in blood (and K+ in urine)
  2. upregulates expression of epithelial Na+ channels (ENaCs) in collecting duct… promotes Na+ absorption
4
Q

How is aldosterone transported in the blood?

A

steroid hormone = lipophilic - needs carrier protein

mainly serum ALBUMIN, to lesser extent TRANSCORTIN

5
Q

How is the RAAS activated?

A

1- decrease in plasma Na+
2- decreased kidney perfusion
3- fall in BP or loss of blood volume (e.g. haemorrhage/dehydration)… sensed by carotid sinus baroRs… increased sympathetic tone to kidney

Cause juxtaglomerular cells of kindey nephrons to release renin into general circulation.

6
Q

What are the effects of renin?

A

cleaves angiotensinogen (constitutively released by liver) to angiotensin I

7
Q

What happens to angiotensin I?

A

cleaved by ACE (angiotensin-converting enzyme) to angiotensin II within lung capillaries

8
Q

How does AngII act to increase BP?

A
  1. potent vasoconstrictor
  2. stimulates adrenal cortex release of aldosterone (which acts on nephron distal tubules and collecting ducts to increase Na+ and H20 reabsorption)
  3. stimulate ADH release from posterior pituitary
9
Q

What are the actions of ADH?

A

induces translocation of aquaporin water channels in PM of collecting duct cells… more water reabsorption

10
Q

What are the most widely used anti-hypertensive drugs acting on RAAS?

A

ACE inhibitors