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Flashcards in Kidney--PCT-->CT Deck (20):

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

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


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

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.


What is reabsorbed in the second half of the PCT?

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


Describe the anion and cation reabsorption in the PCT.

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.


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

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.


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

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


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

Loop Diuretics.


What is reabsorbed in the early distal tubule?

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


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

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


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

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


What are the 2 types of intercalated cells?

alpha--secrete H+ ions
beta--secrete HCO3- ions


What does aldosterone do?

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

alpha intercalated cells--secrete H+


What effect does ADH have on principal cells?

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


Which drug inhibits the insertion of aquaporins?



What are the potassium sparing diuretics?

Aldosterone Antagonists: spironolactone

Inhibit epithelial Na+ channels:


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

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.


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

#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!)


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

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


Rank the substances that are absorbed TF/P

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


What does PTH inhibit in the early PCT?

Na+/PO43- cotransport. causes phosphate excretion.
Think phosphate trashing hormone.