Tubular Reabsorption/secretion Flashcards
Where is the Na+/K ATPase located in the tubular Epithelial cell?
Basolateral membrane
Where is water primarily reabsorbed?
Descending LOH
What ion is used to drive absorption of many solutes such as glucose, amino acids, and phosphates?
Na+
What is solvent drags?
Some solutes such as K+ and Ca++ are entrained in water as it is absorbed paracellularly
Where does reabsorption of HCO3 and secretion of H+ take place?
Proximal tubule
Describe the role of Carbanic anhydrase in glaucoma. What is a potential adverse affec?
- Treaments for glaucoma include Carbanic anhydrase inhibitors as it inhibits production of the aqueous hum our
- Can induce Acidosis
Describe Falconi Syndrome
Impaired absorption in proximal tubule leading to eastern of water, glucose, AAs, bicarbonate, etc in urine
How much of substances get absorbed in the PCT?
100% glucose/AA
80% HCO3
60-70% Na, K, Ca, Cl
60-70% Filtered Water
Describe the osmolality and change in volume in the PCT upon reabsorption
- Isosmotic
- Volume reduced by 2/3
Describe the permeability in the descending loop of Henle.
- High H20 Perm
- Low Ion perm
- No evidence of active transport
Describe permeability in Ascending LOH.
- Low after Perm
2. Active transport of Na/Cl and other ions
How does osmotic concentration change along the loop of Henle?
Filtrate entering descending limb —> Isotonic
Filtrate entering ascending limb is Hyper osmotic
Filtrate exiting the ascending limb is hypoosmotic
What generates positive intraluminal charge of the ascending limb? What does the intraluminal charge drive?
Na/K/Cl Transporter generates intraluminal charge due to K+ backleak nto lumen via channels on apical membrane
Drives reabsorption of calcium
What percentage of Water and Ions is reabsorbed in the loop of Henle?
water - 15%
Ions - 25%
What are the three types of diuretics which work on the kidney?
- Loop diuretics (Na/K/CL transporter)
- Thiazides (Distal tubule NaCl blockers)
- K+ Sparing (Collecting Duct)
How do all diuretics wrk?
- Elevate solute concentration of filtrate
- Tubular lumen water retention from hydration of solutes
- Increased excretion rate
What is the major side affect of furosemide a loop diuretic? Why?
Hyopkalemia
Potassium has other channels into tubular lumen. —
> Excretion of Calcium
What drives paracellular transport of Mg+ into the kidney interstitium?
Positive intracellular potential created by potassium
What is Bartter Syndrome?
- Mutation of Na/Cl/K transporter
- Symptoms similar to loop diuretics
- Polyuria
- Hypokalemia
- Hypercalceuria
- Hypermagnesurea
Describe the function of Thiazides diuretics
Block Na/Cl transporter in early distal tubule
Differentiate Thiazides and loop diuretics.
Loop:
- Na/K/Cl transporter
- Hypokalemia
- Hypercalceuria
- Hypermagnesurea
Thiazides:
- Na/Cl transporter
- Hypokalemia
- ***Hypocalciuria -> Thiazides increase calcium reabsorption
What does Gitelman syndrome mimic?
Thiazides diuretics
What is Fanconi syndrome?
Deficient glucose reabsorption
Why are diabetics frequently urinating and always thirsty?
Glucosuria —> Water reabsorption In tubule
