Renal Regulation of Acid/Base Flashcards

1
Q

What are some entries of acids/bases into body?

A
  • De novo generation from metabolism
  • activity of GI tract
  • processing of ingested food
    • tend to take in more acids, especially processed foods
  • Metabolism of stored fat and glycogen
  • kidneys
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2
Q

What is a buffer?

A
  • Prevents large changes in pH after addition or loss of protons from external sources
  • Not an infinite capacity- once used can’t buffer anymore
  • All body fluids are buffers
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3
Q

What are some intracellular buffers?

A

Protein, phosphate, K/H exchanger

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4
Q

What is our main ECF buffer?

A

HCO3

CO2+H2O–> H2CO3–> HCO3 + H

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5
Q

Which compartment of fluid has largest buffering capacity?

A

ICF (more volume, bigger portion of fluid)

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6
Q

How does the K/H exchanger?

A
  • Depending on concentrations, K and H switch places in order to maintain equilibirium
  • facilitated diffusion
  • If acidotic- H moves into cell, K out of cell
  • If alkalotic- H moves out of cell, K into cell
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7
Q

The concentration of CO2 is essentially _____ and ____ on respiratory system

A

constant; respiratory

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8
Q

Bicarbonates role in acid base?

A
  • made by kidney
  • Freely filtered
  • plasma 24 mmol/L, GFR 180 L/day= 4320 mmol/day filtered load
  • essential that virutally all of filtered bicarbonate is reabsorbed
    • don’t reabsorb bicarb if you’re alkalotic. Most of time, reabsorbing all bicarb
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9
Q

What is the renal handling of A/B?

A
  • Proximal tubule- kidney reabsorb filtered load of bicarbonate (neutral)
    • can also secrete organic bases/ or weak acids under appropraite condition
  • Distal tuuble- kidneys secrete either protons or bicarb to balance net input
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10
Q

What are % of reabsorption of bicarb in diff segments?

A

85% proximal tubule

15% in loop henle/collecting duct (she’s calling it distal tubule)

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11
Q

What happens inside proximal tubule cell to achieve net zero movement in acid/base balance?

A
  • Carbonic anydrase makes H and HCO3 inside cell
  • H moves to apical side H-Na antiporter (H to apical, Na absorbed)
  • Hco3 goes to basolateral side, reabsorbes with Na via Na-HCO3 symptoer or Cl-HCO3 antiporter
  • Bicarbonate filtered from blood has disappeared
  • Its place in the blood has been taken by the bicarb that was produced inside the cell
  • No net change
  • H ion is now water, so does not contribute to urinary excretion of H
  • ON THE PICTURE IGNORE “BLOOD” IT’S WRONG!! THAT IS THE LUMEN OF THE NEPHRON!
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12
Q

What happens to HCO3 molecule in lumen?

A

Excreted (forms with H to turn into CO2 + H2O), but during process, we make additional HCO3 molecule to be absorbed into blood (replacing the molecule we lost)

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13
Q

What occurs in Type A intercalated cells in distal tubule?

A
  • Apical membrane-
    • H-k ATPase (H out to lumen, K into cell)
    • H atpase (out to lumen)
      • H out to lumen combines with HCO3 to make CO2+H2O
  • Basolateral
    • HCO3-Cl antiporter
      • HCO3 into blood
      • Cl into cell
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14
Q

Acid secretion is ____ process

A

active process

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15
Q

How do Type B intercalated cells contribute to acid/base balance?

A
  • Secrete base, only works when we’re alkalotic
  • Apical side
    • HCO3-Cl antiporter (hco3 into lumen, absorb Cl)
  • Basolateral
    • H-K ATPase on apical
    • H- ATPase on apical
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16
Q

What happens if we have too much base?

A

We excrete bicarbonate via type B intercalated cells

17
Q

What happens if we have too much acid?

A
  • Acid load will reduce amount of bicarb in blood
  • kidney replaces lost bicarb by generating new bicarb
  • H ions are secreted and combine with base of buffers other than bicab
    • Other buffers such as phosphate bind with H
  • this generates a new bicarb ion
18
Q

What are titratable acids?

A

All the buffers that H can potentially bind to besides bicarb

  • Only a finite amount of titratable acids
19
Q

What is ammonium’s role in A/B balance?

A
  • Limited amount of titratable acids
  • the rest are excreted attached to ammonium
  • catabolism of protein by liver generated CO2, water, urea, glutamine
20
Q

What is glutamine?

A
  • Created in liver after catabolism of protein
  • taken up by proximal tubule
  • glutamine is converted to bicarb and nh4
  • NH4 is secreted into lumen of proximal tubule and bicarb exits into interstitium
    • for every NH4 into urine, HCO3 goes into blood
21
Q

What is general process a/b regulation in proximal tubule?

A

Reabsorbs bicard

produces ammonium

22
Q

What happens with A/B Balance in loop of henle?

A

Reabsorb Bicarb in ascending loop

23
Q

What happens with a/b balance in distal and CD?

A

Reabsorbs bicarb

secretes bicarb

24
Q

What is equation for net acid excretion?

A

TA + NH4- HCO3

TA + NH4= excreted acids

Tells HCO3 gain/loss from body

25
Q

What happens to NH4 and TA during acid load

A
  • NH4 excretion goes way up
  • TA excretion increases a little
  • Net acid excretion goes up significantly
26
Q

What happens to NH4 and TA, and HCO3 excretion levels in base load?

A
  • Excrete higher amount HCO3
  • Negative net acid secretion
  • Little bit of NH4 excretion
27
Q

Acidosis can result from either?

A

gain of acid or loss of bicarb

28
Q

What causes acid gain? Base loss?

A
  • Acid gain-
    • decreased respiration- increased CO2
    • keto acids- byproduct of naerobic metabolism, fuel source when glucose decreases
    • renal failure- acid gain because kidney cannot remove acid from body
  • Base loss
    • diarrhea- normal reabsorb HCO3 in intestine with K, in diarrhea, moving too fast to reabsorb bases
29
Q

What is the anion gap? What does it tell us?

A
  • Sum of cation-sum of anions
  • tell us if we have acid gain or base loss
  • normal 8-12
    • If acidotic, but AG is normal- means that you had loss of base
    • If acidotic and AG >12- means you had gaine of acid
30
Q

What situations in body would lead to alkalosis?

A
  • Results from loss of fixed acid or gain of HCO3
  • Loss of fixed acid
    • hyperventilation
    • vomiting
  • Gain of HCO3
    • bicarb overdose (tums)
    • chronic diuretic usage
31
Q

The concentration of metabolic acids and HCO3 is regulated by the

A

kidney

32
Q

How does the anion gap not change when you have an acidosis?

A
  • The lost bicarb is replaced by Cl- so anion gap does not change!
  • This means you have a loss of base
33
Q

What are the 2 processes that the kidneys regulate HCO3 concentrations?

A
  1. Reabsorption of filtered HCO3
  2. Gneration of new HCO3