Kidney--PCT-->CT

Question 1

Which things are reabsorbed in the first half of the PCT?

Answer 1

All of glucose and AA (and Pi or lactate) via co-transporter w/ Na+
2/3 of fluid–>isotonically (water follows electrolytes)
Bicarb reabsorbed

Question 2

Describe in detail how bicarb is reabsorbed in the first half of the PCT?

Answer 2

bicarb and H+ in lumen combines to form CO2 and water via carbonic anhydrase.
Taken up into cell.
Carbonic anhydrase breaks into HCO3 & H+.
H+ is secreted back into lumen.
Bicarb is reabsorbed via cotransporter w/ Na+ & countertransporter w/ Cl-.
Ultimately, driven by Na+/K+ ATPase.

Question 3

What is reabsorbed in the second half of the PCT?

Answer 3

Cl- and Na+ reabsorption driven by Na+/K+ ATPase

Question 4

Describe the anion and cation reabsorption in the PCT.

Answer 4

Anion reabsorption is facilitated via alpha-ketoglutarate (counter)
*ultimately driven by Na+/K+ ATPase.

3Na+ are pushed into blood for 2K+ being pushed into cell. Relative neg. charge in cell. Attracts cations via this electrochemical gradient.
Then cations are exchanged for H+ and pushed into the lumen.

Question 5

Describe what is reabsorbed in the thin descending limb of the loop of Henle.

Answer 5

Water is reabsorbed here.
Impermeable to Na+.
Luminal fluid becomes more concentrated by end of this limb.
The water leaves via osmotic gradient b/c interstitium down there is super concentrated.

Question 6

What is reabsorbed in the thick ascending limb of the loop of Henle?

Answer 6

Na+/2Cl-/K+ cotransporter (active)
Impermeable to water.
Ca++ and Mg+ also reabsorbed. (b/w cells)
Produces a more dilute filtrate.

Question 7

What class of drugs inhibits the Na+/2Cl-/K+ cotransporter in the thick ascending limb?

Answer 7

Loop Diuretics.

Question 8

What is reabsorbed in the early distal tubule?

Answer 8

Some reabsorption of Na+ & Cl-
Not always impermeable to water
Ca++ reabsorption happens here under the control of PTH.

Question 9

What are the 3 ways that PTH increases serum Ca++?

Answer 9

1. stimulates osteoclasts
2. stimulates kidneys to activate vit D
3. stimulates kidneys to reabsorb more Ca++ in the DCT.

Question 10

What are the 2 types of cells in the DCT? What do they reabsorb?

Answer 10

principal cells: most abundant, reabsorb H2O and Na+, Secrete K+
intercalated cells: secrete H+ ions or secrete HCO3-. Reabsorb K+

Question 11

What are the 2 types of intercalated cells?

Answer 11

alpha–secrete H+ ions

beta–secrete HCO3- ions

Question 12

What does aldosterone do?

Answer 12

targets principal cells–>Na+ reabsorption, K+ secretion. Water will be naturally reabsorbed here.

alpha intercalated cells–secrete H+

Question 13

What effect does ADH have on principal cells?

Answer 13

activates these cells via V2 and inserts aquaporins. Water reabsorption!!

Question 14

Which drug inhibits the insertion of aquaporins?

Answer 14

Lithium

Question 15

What are the potassium sparing diuretics?

Answer 15

Aldosterone Antagonists: spironolactone
eplerenone

Inhibit epithelial Na+ channels:
triamterene
amiloride

Question 16

Describe the TF/P chart. What does it mean to be =1? >1?

Answer 16

looks at the conc’n of a substance in the tubular fluid v. plasma.
TF/P=1 is a substance that is reabsorbed in the same way as water.
TF/P>1: solute is reabsorbed less quickly than water.
TF/P

Question 17

Rank the substances that are absorbed TF/P>1.

Answer 17

#1: PAH (b/c also super secreted)
Creatinine (b/c not reabsorbed, and a little secreted)
Inulin (b/c not reabsorbed or secreted)
Lower--Urea (wanna get rid of it!)
Cl-

Question 18

Rank the substances that are absorbed TF/P=1.

Answer 18

water

a little higher Na+, a little higher is K+

Question 19

Rank the substances that are absorbed TF/P

Answer 19

Most neg.
Glucose (really want this, gotta reabsorb!)
Amino Acids
HCO3-
Pi (closer to TF/P=1)

Question 20

What does PTH inhibit in the early PCT?

Answer 20

Na+/PO43- cotransport. causes phosphate excretion.

Think phosphate trashing hormone.