Lecture 8 - Nutrients, K+, Ca++, Mg++, and Phosphate

Question 1

Glucose (and basically ALL “nutrients”) is completely reabsorbed within the ______ of the Nephron. In the Early _____, it is reabsorbed via the _____ cotransporter, while in the Late _____ it is reabsorbed via the ______ cotransporter. Which cotransporter moves 2 Na+ per Glucose?

Answer 1

PCT

Early PCT –> SGLT2

Late PCT –> SGLT1

SGLT1 –> 2 Na+ per Glucose

Question 2

_______ inhibits both SGLT1 and 2, so it used to be used as a treatment for Type 2 diabetes. However, it has poor bioavailability and is potentially toxic. Instead, Canagliflozin, which blocks ______, has been approved for DM type 2 treatment –> it is associated with moderate weight loss, increased risk of _____, and may cause mild UTIs.

Answer 2

Phlorizin

SGLT2

Dehydration

Question 3

An increase in plasma concentration of K+ results in both rapid and slow compensatory mechs. What are the rapid vs slow mechs?

Answer 3

Rapid –> uptake of K+ into cells (insulin stims Na/K ATPase –> K+ moves into muscle cells and Epi acting on Beta 2 receptors does the same ).

Slow –> Kidney Excretion (occurs on the order of hours.)

Question 4

In the Kidney, 60% of K+ is reabsorbed in the ______ via ______ transport. Another 30% is reabsorbed in the _____ via the Na/K/Cl cotransporter and _____ transport. Minor amounts are reabsorbed by Type A _____ cells via K+/H+ ATPase.

Answer 4

PCT

Paracellular

TAL

Type A Intercalated cells

Question 5

Remember that ______ cells in the Collecting duct are the main cells responsible for K+ SECRETION.

Keep in mind that Loop and Thiazide diuretics increase urine flow. What effect does this have on K+ loss?

On the other hand, ______ (ENaC blocker) and Spironolactone (an Aldosterone antagonist) are K+ SPARING diuretics.

Answer 5

Principal cells

They increase K+ secretion/excretion.

Amiloride and Spironolactone

Question 6

Aldosterone secretion can be triggered by increased plasma K+ concentration. ______ cells are sensitive K+ sensors, responding to changes of 0.5mM.

Answer 6

Glomerulosa

Question 7

Does Hypo or Hypercalcemia cause hyper-reflexia and Laryngospasm? Why?

Answer 7

HYPOcalcemia

It is because it lowers the required depolarization for APs –> cells become hyperexcitable

Question 8

65% of Ca++ reabsorption occurs in the _____ via _____ transport.

25% occurs in the TAL, again mostly via ______ transport driven by POSITIVE lumenal charge.

The DCT is responsible for about 8% via _______ transport (keep in mind both the TAL and DCT Ca++ reabsorption is regulated by _____).

Answer 8

PCT

Paracellular

Paracellular

Transcellular

PTH