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1
Q

Proximal Tubule Reabsorption

A
  1. Active transport Na creates intracellular (-) allowing intracellular movement of Na
  2. H+ is secreted into the lumen by Na-H Exchanger
  3. H+ combines with filtered HCO3 -> H2CO3 -> H2O + CO2
  4. CO2 diffuses into the cell to combine with H2O to form H2CO3 -> H+ + HCO3
2
Q

Renal Threshold for Bicarbonate Absoprtion

A

25mM before it starts being excreted

3
Q

Titratable Acid in Urine

A

H2PO4

4
Q

What is responsible for forming Bicarbonate?

A

Distal Tubule

5
Q

Function: Intercalated Cell

A

Secretes hydrogen ions into the filtrate

6
Q

Function: Principal Cells

A

Hormonally regulated water and sodium reabsorption

Potassium secretion

7
Q

Diffefence: Alpha and Beta Intercalated cells

A

A: H+ Excreted through H+-ATPase Pump
B: Active when you remove Bicarbonate

8
Q

Two Characteristics of Hyperaldosterone

A

Hypokalemia

Hypertension

9
Q

Secretion of H+ by the Alpha-Intercalated Cell at the Cortical Collecting Tubule

A
  1. Intracellular H2O and CO2 in the presence of Carbonic Anhydrase form H+ and HCO3-
  2. H+ secreted by an active H+ATPase Pump
  3. HCO3 returns to circulation via Cl-HCO3 exchanger
  4. Formation of NH4+
  5. Formation of Titrable Acid
10
Q

Define: Ionic Trapping

A

Ammonia can freely leave the Collecting Duct because it is uncharged. Once this passes into the lumen, it combines with Hydrogen ions to become NH4+ and can no longer return

11
Q

Differentiate NH3 and NH4+

A

NH3: Base Form, Uncharged, Permeable
NH4: Charged, Impermeable

12
Q

Regulation of HCO3 reaborption

  1. Primary
  2. Secondary
A

P: Systemic Acid Base Balance

S:

  • Increase in filtered load of HCO3
  • Decrease in ECF volume
  • Increase in Angiotensin II
  • Hypokalemia
13
Q

How to test the amount of H+ produced during HCO3 formation?

A

Titrate with Sodium Hydroxide until pH = 7.4

14
Q

Fates of Secreted H+

A

90% Titrates filtered Bicarbonate in Reclamation
1% Buffered by NH3
1% Buffered by other Tubular Buffers, mostly HPO4
Minute amount remains free