05.07 - Loop, DT, CD (Rao) - PP, LG, No reading, Not watched Flashcards
What is driving force for NaCl reabsorption in ThinAL
Osmotic Gradient
Why is Cl reabsorbed in DCT/CD
Na reabsorption is greater than K secretion, therefore Cl is reabsorbed
What drives Bicarb/Cl exchanger in DCT/CD
Increase in intracellular Bicarb
Which has bicarb channel in luminal membrane: alpha or beta intercalate
Beta
Under high acidosis conditions, DCT/CD cells express new
H transporter: H-K ATPase or Proton Pump
Permeability of TDL to NaCl, Urea, Water
Minimal for NaCl and Urea, Highly permeable to water
Active transport in Thin Ascending and Thin Descending Limbs
None
Liddle’s Syndrome is characterized by
Increase Na reabsorption and K secretion
How does Aldosterone increase Na reabsorption
(1) Increases number of luminal Na channels; (2) Increases basolateral Na/K; (3) Increases ATP synthesis
On which parts of nephron does Aldosterone act
DCT/CD
How does Na reabsorption affect K secretion in DCT/CD
Decrease Na reabsorption results in higher lumen-negative transepithelial voltage = K secretion
% of filtered load received by DCT/CD of Water, NaCl, KCl, and Urea
10%, less than 10, less than 10, 50
Where is the Na-Cl transporter present
Only in DCT
What is Conn’s Syndrome
Aldosterone secreting tumore
Amiloride and Triamterene block
Electrically conductive Na channels
How does Aldosterone affect K
Increases secretion in DCT/CD
What is Addison’s disease
Complete absence of Aldosterone
How does plasma Ang 2 affect Aldosterone secretion
Low plasma AngII Decreases Aldosterone secretion
Where is the electrically conductive Na channel present
In both DCT and CD
Which has proton channel in luminal membrane: alpha or beta intercalated
Alpha
Electrical acivity of electrically conductive Na channel
Makes lumen more negative; Membrane is depolarized
ADH stimulates what in ThickAL
Na-K-2Cl cotransporter (and thus reabsorption of Na)
Aldosterone increases what 3 channels
(1) Na/K ATPase; (2) Luminal K; (3) Lumina Na
What do Thiazide diuretics block
Na-Cl cotransporter
NaCl reabsorption in ThinAL
Strong: 2/3 received volume
What blocks Na-K-2Cl cotransporter
Loops
Major luminal transporter in ThickAL
Na-K-2Cl
Which cell type exchanges Na and K
Principal Cells
Osmolarity change in ThinAL
Drops due to loss of NaCl
Epithelial cells in ThickAL
Thick, many mitochondria
Epithelial cells in ThinAL
Thin, few mitochondria
How does plasma K affect Aldosterone secretion
Increased plasma K increases Aldosterone secretion
___ increases flow and Na output into distal tubule, therefore, ___
Loop diuretics, Increase K secretion
Which cell type exchanges H+ and Bicarb
Alpha-Intercalated
2 Regulatory factors of K secretion in DCT/CD
Increased flow by diuretics inc. K secretion; Decreased Na reabsorption (diuretics) results in higher lumen-negative transepithelial charge
Maximum of 1200 mOsm is due to what components
600 mOsm Urea, 600 mOsm NaCl
How is switch of H-ATPase and HCO3-Cl exchanger achieved
Activation of two types of intercalated cells
Where do Furosemide and Bumetanide act
Cl site in N-K-2Cl cotranspoter in ThickAL
How do plasma ACTH levels affect Aldosterone secretion
Low plasma ACTH levels decrease Aldosterone secretion
What stimulates Na-K-2Cl cotransporter
ADH
3 other channels in ThickAL besides Na-K-2Cl and Na-K
Basolateral Cl channel (reabsorb); Basolateral K-Cl cotransporter (reabsorb); Apical K (secrete)
How is Bicarb reabsorbed in DCT/CD
Bicarb/Cl exchanger
How is H+ secreted into lumen in DCT/CD
Active transport (against high gradient)
___ prevent membrane depolarization; no increase in ___
Amilorides, K secretion
How does increased flow to DT/CD affect K secretion
Increases
2 transport mechanisms for Na reabsorption in DCT/CD
Electrically conductive Na channels; Na-Cl cotransporter
Net result of DCT/CD action if impermeable to water
Dilution of Urine
3 Manifestations of Conn’s Syndrome
Hypokalemia, Hypernatremia, HTN
Under Alkalosis conditions, what channels switch directionality
H-ATPase and HCO3-Cl exchanger
2 differences between H+ secretion in proximal vs distal
In distal, H+ is secreted against high gradient actively; Also, distal epithelium is impermeant to diffusion
What does Addison’s disease tell us about Na reabsorption and K secretion
Not entirely dependent on Aldosterone
___ block electro-neutral Na transport, without ___
Thiazides, affecting membrane depolarization
What generates H+ in DCT/CD
Cellular Carbonic Anhydrase
What blocks the Na-Cl cotransporter
Thiazide Diuretics
What blocks the electrically conductive Na channels
Amiloride, Triamterene
Reabsorption/Secretion of Na, K, Cl in DCT/CD
Na actively reabsorbed, K is secreted, Cl is reabsorbed
Permeability of TAL to NaCl, Urea, Water
Extremebly water impermeable, Impermeable to Urea, Permeable to NaCl
Driving force for Na-K-2Cl transporter
Na electrochemical gradient (set up by Na-K ATPase)
