L7: Integration of salt and water balance

Question 1

The RAA system ________ Na+ retention

Answer 1

promotes

Question 2

JGA glomerular cells -> Renin (______) ->

Answer 2

(protease) -> cleaves angiotensinogen C-terminus -> release angiotensin I -> ACE cleaves Ang I -> Active Ang II

Question 3

ACE is abundant in:

Answer 3

luminal surfaces of vascular endothelial cells

Question 4

What are the stimulus’ for renin release?

Answer 4

1. Baroreceptors detect decreased renal blood pressure -> increased sympathetic effect on JGA -> Renin releases.
2. Decreased GFR -> Decreased NaCl delivery/concentration to macula densa cells -> Renin release
3. Decreased renal perfusion pressure -> Renal baroreceptors of afferent arteriole granular cells detects decreased distension -> Decreased intracellular Ca2+ -> Renin release

Question 5

Effects of angiotensin II

Answer 5

• Stimulates adrenal cortex to release aldosterone.
• Vasoconstriction of the efferent and afferent arterioles but efferent to a greater degree
• Increased tubuloglomerular feedback -> increase in Na+ and fluid delivery to the macula densa
  elicits a more pronounced fall in the (GFR).
• Increased stimulation of transporters (Na-K ATPase, NHE, Na-HCO3 symporter)
• Stimulates thirst and AVP release by binding to hypothalamus

Question 6

Explain the effects of angiotensin II acting on the afferent and efferent arterioles

Answer 6

• Reduced hydrostatic pressure in downstream peritubular capillaries -> Increased gradient for Na+ absorption in the thin ascending limb
• Increased filtration fraction -> Increased protein concentration in blood downstream -> Increased colloid osmotic pressure in peritubular capillaries -> Increases water reabsorption

Question 7

Effects of ANP

Answer 7

Increase GFR, Increase cortical and medullary blood flow, Decreased renin, Decreased AVP

Question 8

Effects of aldosterone

Answer 8

Aldosterone is lipid soluble -> diffuses through basolateral cell membrane -> Binds to MR -> Aldosterone-MR complex diffuses into nucleus and induces genes that code for mitochondrial enzymes and membrane transport proteins (Na-K, ENac, Na-HCO3)

Question 9

ENac embeds in the ________ membrane

Answer 9

apical

Question 10

________ inhibits ENac

Answer 10

amiloride

Question 11

_________ inhibits MR

Answer 11

spirinolactone