Tubular reabsorption and secretion Flashcards
What are the different mechanisms of transport across a cell membrane?
Diffusion
Uniport
Symport/cotransport
Antiport
Ion channel
Active transport
What are common characteristics of protein mediated transport?
Rate of transport
Saturation kinetics
Chemical specificity
What is the plasma threshold of glucose where the excretion from the kidneys begins?
200 mg/dL
Where is the Na/H antiporter located in the kidneys?
Proximal tubule
Where is H+ secreted in the kidney?
Proximal tubule
Thick ascending limb
Alpha-intercalated cells in collecting tubule
Where is bicarbonate synthesized in the kidney?
Proximal tubule
Alpha intercalated cells in collecting tubule
What is the affect of angiotensin II in the proximal tubule?
Stimulates Na/H countertransport
What is the site of action of osmotic diuretics?
Proximal tubule - Na/H countertransport
What are the osmotic diuretics?
Urea
Glucose
Mannitol
What is the site of generation of the medullary osmotic gradient?
Thick ascending loop of Henle
What is the site of action of loop diuretics?
NKCC2 transporter in the loop of Henle
What tubules are impermeable to water?
Thick ascending loop of Henle
Early distal tubule
When does tubular fluid become hypotonic?
Early distal tubule
What is the site of action of thiazide-like diuretics?
Early distal tubule - blocks Na/Cl cotransporter
What does membrane permeability to water in the principal cells depend on ?
Concentration of ADH
What stimulates Na/K antiport in the principal cells?
Aldosterone
Where are renal principal cells located?
Late distal tubules and cortical collecting tubules
What is the site of action for K sparing diuretics?
Principal cells
What is the general movement of sodium through the kidney?
Freely filtered
99.5% reabsorbed
0.5% excreted
What does potassium excretion depend on?
Rate of potassium excretion by principal cells
About how much of filtered calcium is normally excreted?
Less than 1%
About how much filtered phosphate is normally excreted?
About 15%
Where is urea reabsorbed in the kidney?
PCT
Collecting duct
Where is urea secreted in the kidney?
Thin descending limb
What is the defect in Fanconi syndrome?
Impaired reabsorption in proximal tubule
What are the effects of Fanconi syndrome?
Metabolic acidosis
Hypophosphatemia
What is the defect in Bartter syndrome?
NKCC2 cotransporter
What are the effects of Bartter syndrome?
Metabolic alkalosis
Hypokalemia
Hypocalcemia
What is the defect in Gitelman syndrome?
Na/Cl transporter in DCT
What are the effects of Gitelman syndrome?
Metabolic acidosis
Hypokalemia
Hypercalcemia
What is the defect in Liddle syndrome?
Overactive ENaC in collecting ducts
What are the effects of Liddle syndrome?
Metabolic alkalosis
Hypokalemia
Hypertension
Hypoaldosteronism
What are lost when using osmotic diuretics?
Unabsorbed sugars, sodium, water
What is the effect of carbonic anhydrase inhibitor in the kidney?
Decreased reabsorption of HCO3-
Decreased Na/H exchange
What is lost when using loop diuretics?
Calcium
Potassium
Water
What is lost when using thiazide-like diuretics?
Potassium
What group of diuretics are calcium sparing?
Thiazide-like diuretics
What is the primary action of diuretics?
Decrease plasma osmolality
What is the secondary action of diuretics?
Increase water excretion
