Urinary 2 - Renal reabsorption Flashcards
Where does the majority of reabsorption occur?
Proximal Convoluted Tubule
Where does 65% H2O reabsorption occur?
PCT
Where does 100% Glucose and amino acid reabsorption occur?
PCT
What channel in the basolateral membrane drives renal reabsorption?
Na+/K+-ATPase
Name the 2 Na+ channels located on the apical membrane of the PCT:
1 - Na+-Glucose symporter (SGLUT)
2 - Na+/H+ antiporter
Name the Na+ channel located on the apical membrane of the TAL (LoH):
Na+/K+/2Cl symporter (NKCC2)
Name the Na+ channel located on the apical membrane of the early Distal Tubule:
Na+/Cl- symporter (NCC)
Name the Na+ channel located on the apical membrane of the late distal tubule and collecting ducts:
ENaC
What substances are secreted into the tubules?
- K+
- H+
- Organic anions and cations
How do anions and cations move across the apical membrane (to be secreted)?
via H+ antiporter
Name a few endogenous cations that are secreted into the tubule:
- Acetylcholine
- Dopamine
- Adrenaline
- Histamine
- Serotonin
Name a few drugs that are secreted into the tubule:
- Sulfonamines
- Morphine
- Atropine
- Isoproterenol
- Penicillin
- Salicylate
- NSAIDs
Name a few endogenous anions that are secreted into the tubule:
- Urate
- Bile salts
- Fatty acids
How are the majority of Cl- reabsorbed in the PCT?
via passive paracellular movement in S2/3 segment, down concentration gradient (no Cl- reabsorption in S1 segment)
In which part of the tubule does 67% of Na+ reabsorption occur?
PCT
Name the 3 driving forces for reabsorption from the PCT into the peritubular capillaries:
1) Osmotic gradient
2) Oncotic force (higher in peritubular capillary due to lack of protein in tubule)
3) Hydrostatic pressure (higher in interstitium, pushes solute into capillary)
What is the name of the structure which invaginates the glomerulus?
Bowman’s Capsule
Name the 2 types of nephrons:
1) Juxtamedullary
2) Cortical
What type of nephron is most common?
Cortical (80%)
How is the histology of the thin ascending LoH different to the PCT, and why?
In thin ascending LoH: - no brush border - no mitochondria - wider lumen No active transport in thin ascending LoH (^active transport in PCT)
Name the main ions reabsorbed in the distal tubule:
Na+
Ca2+
Cl-
What is reabsorbed in the descending LoH?
Only H2O
In what part of the ascending LoH does active transport occur?
Thick ascending limb (TAL)
What part of the nephron uses most energy, therefore is most susceptible to hypoxia?
Thick ascending limb of LoH (TAL)
Name the channels in the basolateral membrane of TAL (Thick ascending limb of the LoH):
Cl- channel
Na+/K+-ATPase
K+/Cl- cotransporter
Name the channels on the apical membrane of TAL (Thick ascending limb of the LoH):
Na+/K+/2Cl symporter (NKCC2)
ROMK
What is ROMK, and in what part of the tubule is it present?
Renal Outer Medullary K+ channel
TAL (Thick ascending limb of LoH)
What percentage of Na+ is reabsorbed in the PCT?
67%
What percentage of Na+ is reabsorbed in the TAL (Thick ascending limb of LoH)?
25%
What is the main driving force for the active reabsorption of Na+ and Cl- in the ascending limb of LoH?
Concentration gradient
Due to concentration of Na+ and Cl- in the descending limb (only H2O reabsorption)
What part of the tubule is the main site of Ca2+ reabsorption?
Distal convoluted tubule
What happens to Ca2+ once it has been reabsorbed into the tubular cell?
- Binds to Calmodulin
- Moves across basolateral membrane via NCX
What regulates Ca2+ reabsorption from the tubule lumen?
PTH
1,25-OH2 Vitamin D (Calcitriol)
Is the fluid entering and leaving the Distal convoluted tubule hypo- or hyper-osmotic?
Hypo-osmotic
Name the tubular cells lining the cortical collecting duct:
- Principle cells (70%)
- alpha Intercalated cells
- beta Intercalated cells
Name the most common cell lining the cortical collecting duct:
Principle cells
What ions are reabsorbed/secreted by the principle cells (lining the cortical collecting duct):
Na+ and Cl- are reabsorbed
K+ is secreted
Describe the mechanism of Na+ and Cl- reabsorption across Principle cells:
Na+ is reabsorbed across the apical membrane via ENaC, and across the basolateral membrane via Na+/K+-ATPase
This drives paracellular Cl- uptake (due to electrochemical gradient)
What ions are secreted from Principle cells, and via which channel?
K+
ROMK
Name the cells of the cortical collecting duct which secrete acid:
alpha Intercalated cells
Name the channels in the apical membrane of alpha intercalated cells:
ACID SECRETING CELLS:
- H+-ATPase
- H+/K+-ATPase
Name the cells of the cortical collecting duct which secrete bicarbonate:
beta Intercalated cells
Name the channels on the apical membrane of beta Intercalated cells:
BICARBONATE SECRETING:
- Na+/Cl-/HCO3- exchanger
- Cl-/HCO3- exchanger
What part of the tubule is lined by intercalated cells?
Cortical collecting duct
