L54 Flashcards
What layer of the kidney contains the glomeruli?
Cortex
What is the basolateral transporter for Na reabsorption in the prox tubule?
3Na out (into blood) // 2K into cell ATPase Active transport
What limits the amount of Na that is reabsorbed in the PCT?
Glomerulotubular balance - reason limited effectiveness of PCT diuretics
As you pull off volume, you incite this mechanism
Not about the increase in bicarb in the urine due to carbonic anhydrase inhibitors
How reabsorb bicarb at PCT?
Freely filtered - PCT impermeable to bicarb
Carbonic anhydrase in the brush border: bicarb -> CO2
CO2 diffuses across
CO2 + H2O = bicarb + H
Bicarb reabsorbed, H secreted into urine
HCO3- absorption = H secretio n
Explain the mechanism + effects of carbonic anhydrase inhibitors. Name the drug you need to know.
Acetazolamide
Lose bicarb in urine -> non-gap metabolic acidosis
What are the PCT organic acid transporters? How do you measure if they are working or not?
OCT = cation OAT = anion Para-amino-hippurate = 100% secreted into urine via transporters
Name + explain the drug that targets PCT organic acid transporters.
Probenecid - inhibits OAT 1
1ary use for gout - keeps uric acid in urine
Also extend life of antibiotics elim in the urine
What is the fxn of the descending limb of the LOH?
H2O perm + imperm to electrolytes = concentrating
What is the fxn of the ascending limb of the LOH?
H2O imperm + perm to electrolytes = diluting
Why is the thick ascending loop thick?
Cells have ↑mitochondria (v metabolically active)
What is the apical vs basal Na transporter in the thick ascending LOH?
Apical = Na/K/2Cl
Low [Na] in cells, moves down [ ] to get inside, pushed out via:
Basal = N/K ATPase
What happens to K in the thick ascending LOH?
Cycles into urine via ROM K
Explain how Na is reabsorbed paracellularly in the thick ascending LOH.
Bringing Cl into cells via 2Cl/Na/K
Hyperpolarizes the BL membrane
Drives reabsorption of Na between cells
Mechanism of loop diuretics
Direct: X 2Cl/Na/K Indirect: elim trans-tubular potential from Cl that drives paracell absorption Na 1. Can't [ ] urine 2. Large volume output "Can't concentrate or dilute your urine"
What the Uosm on loop diuretics?
Isosthenuria = same as plasma
Where is the macula densa? How does it work?
End of thick ascending LOH
Senses [Cl-] in urine as determinant of flow
Low -> release renin (thinks low flow = underprofused)
What is the role of DCT?
- Final dilution = H2O imperm while reabsorbing NaCl
- Ca reabsorption
- Apical = Ca channel
- BL = Ca/3Na transporter
Explain the mechanism of diuretics that work at the DCT
Thiazides
X apical NaCl cotrans
↑Ca reabsorption
Can no longer dilute urine - lose salt AND water
Where and how does aldosterone act in kidney?
Cortical CD
↑ENAC - water follows
Have to excrete K into urine this way to keep charge neutral
3 factors that det K excretion rate
- Lumen (-) due to Na absorption
- Fluid flow rate - determines [K] in the urine
- Aldosterone via ENAC
What 2 diuretics directly block ENAC
Amiloride
Triamterene
What diuretic blocks aldosterone directly
Sprionolactone
What diuretic blocks the aldosterone receptor
Eplerenone
What diuretic works at the medullary CD?
V2 antagonists = vaptans
Block ADH action - no water reabsorption
How does ADH increase with water deprivation vs vol depletion?
Water deprivation: LINEAR ↑ADH
Vol depletion: EXP ↑ADH
