Lecture 15: Renal Physiology Part 3 Flashcards
What is a diuretic?
Agent that increases urine volume
What is a natriuetic?
Increase in renal sodium excretion
-also increases water excretion
What is reabsorbed in the proximal tubule?
Sodium Bicarbonate Sodium Chloride Glucose (almost all) Amino Acids (almost all) Potassium Organic Solutes Urea
How is potassium reabsorbed in the proximal tubule?
Paracellular pathway (between cells)
How is water reabsorbed in the proximal tubule?
Passively
What promotes the reabsorption of sodium bicarbonate?
Na+/H+ exchanger (NHE3)
-luminal membrane of proximal tubule epithelial cell
How is sodium reabsorbed into the capillaries?
Na+/K+ ATPase on basolateral membrane of proximal convoluted tubule
Where are diuretics delivered to?
Luminal side of tubule (apical) where they act
What do carbonic anhydrase inhibitors do?
Inhibit carbonic anhydrase
- decrease in H+ formation inside PCT
- decrease in Na+/H+ transport
- Increase in urine pH
- Decrease in body pH
What is reabsorbed from the thin descending limb of the loop of Henle?
Water
What is reabsorbed from the thick ascending limb of the loop of Henle?
Sodium Potassium Chloride Magnesium Calcium
How is sodium reabsorbed in the thick ascending limb of the loop of Henle?
Na+/K+/2Cl- Cotransporter
-establishes ion concentration gradient
How are magnesium and calcium reabsorbed in the thick ascending limb of the loop of Henle?
Diffusion of potassium back into tubular lumen drives reabsorption of cations via paracellular pathway
What do loop diuretics do?
Inhibit Na+/K+/2Cl- cotransporter in thick ascending limb of the loop of Henle
- decreased intracellular concentration of potassium, sodium, and chloride in thick ascending limb
- decreased reabsorption of calcium and magnesium
- increased diuresis
- Decrease in urine pH
- Increase in body pH
What is reabsorbed in the distal convoluted tubule?
Sodium chloride
Calcium
How is sodium reabsorbed in the distal convoluted tubule?
Thiazide sensitive Na+/Cl- cotransporter (NCC)
-found on apical side of DCT
How is calcium reabsorbed in the distal convoluted tubule?
Passively
-regulated by parathyroid hormone
What do thiazide diuretics do?
Inhibit Na+/Cl- cotransporter (NCC)
- Increased luminal sodium and calcium concentration
- Increased diuresis
- Decrease in urine pH
- Increase in body pH
What is reabsorbed from the collecting duct?
Sodium chloride
What is secreted into the collect duct?
Potassium
Hydrogen
What role does aldosterone play at collecting duct?
Increases expression of ENaC to increase sodium reabsorption and promote potassium secretion
-also causes retention of water
What role does vasopressin play at collecting duct?
1) Increases water permeability: Inserts aquaporin-2 on apical membrane of principal cells on collecting duct to promote water reabsorption
2) Increase urea permeability in IMCD
3) Increases activity of Na+/K+/2Cl- Cotransporter in thick ascending limb
What do K+ sparing diuretics do?
Inhibition of aldosterone receptor
- decreased ENaC: more sodium excreted and less potassium excreted
- Increase in urine pH
- Decrease in body pH
What stimulates sodium reabsorption?
Low sodium levels
Severe diarrhea
Angiotensin II
Aldosterone
What stimulates sodium secretion?
Increased ECF sodium levels
Increased tubular flow rate
What stimulates potassium reabsorption?
Low potassium levels
Severe diarrhea
What stimulates potassium secretion?
Increased ECF potassium levels
Aldosterone
Increased tubular flow rate
Sodium delivery to cortical collecting duct
During anti-diuresis, where is urea concentrated?
Inner medullary collecting duct
-promotes a passive reabsorption down its concentration gradient to interstitium to loop of henle
