ADD Gene models + nephron function (3)

Question 1

What 2 types of cell are the late distal tubule and cortical collecting duct made up of?

Answer 1

-principal
-intercalated

Question 2

What are the 2 types of intercalated cell?

Answer 2

-alpha intercalated cell
-beta intercalated cell

Question 3

What do the alpha and beta intercalated cells do?

Answer 3

-alpha - H+ secretion and HCO3- reabsorption
-beta - H+ reabsorption + HCO3- secretion

Question 4

How does transport occur across the principal cell?

Answer 4

-Na+ moves out + K+ in via ATPase on basolateral membrane
-Na+ moves in via ENaC protein on apical membrane
-K+ moves out via ROML on apical membrane (stays in urine) + via Kir2.3 on basolateral membrane
-H2O moves in via aquaporin 2 on apical membrane + out via aquaporins 3 + 4 on basolateral membrane

Question 5

What diuretic works on cells in the late distal tube + CCD and how?

Answer 5

-amiloride
-blocks ENaC to prevent sodium reabsorption, inhibiting water reabsorption
-excrete more sodium + water, decreasing blood volume
-treatment for high blood pressure

Question 6

What are diseases that affect the principal cells of the late distal tubule and CCD?

Answer 6

-diabetes insipidus
-Liddle’s syndrome

Question 7

What is diabetes insipidus?

Answer 7

When you struggle to concentrate the urine

Question 8

Describe Liddle’s syndrome

Answer 8

-affects ENaC inheritance
-dominant inheritance
-retain too much sodium, so reabsorb more water, leading to hypertension
-hypokalaemia

Question 9

Where do mutations occur to cause Liddle’s syndrome?

Answer 9

-in COOH tail of beta or gamma subunits
-deletes proline rich motifs

Question 10

What does excessive sodium transport as a result of Liddle’s syndrome do to water reabsorption?

Answer 10

-more ENaC channels causes more sodium transport
-driving force for water reabsorption increased
-expansion of extracellular fluid volume + cardiac output
-mean arterial pressure = cardiac output x heart rate

Question 11

What does excessive sodium transport as a result of Liddle’s syndrome do to potassium secretion ?

Answer 11

-more ENaC channels causes more sodium transport
-driving force for potassium secretion increased
-lose potassium in urine - hypokalaemia

Question 12

What is treatment for Liddle’s syndrome?

Answer 12

-amiloride
-inhibitor of ENaC

Question 13

How does transport across alpha intercalated cells work?