Renal Regulation of Acid/Base Flashcards Preview

Physio Test 4 > Renal Regulation of Acid/Base > Flashcards

Flashcards in Renal Regulation of Acid/Base Deck (33)
Loading flashcards...

What are some entries of acids/bases into body?

  • 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


What is a buffer?

  • 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


What are some intracellular buffers?

Protein, phosphate, K/H exchanger


What is our main ECF buffer?


CO2+H2O--> H2CO3--> HCO3 + H


Which compartment of fluid has largest buffering capacity?

ICF (more volume, bigger portion of fluid)


How does the K/H exchanger?

  • 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


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

constant; respiratory


Bicarbonates role in acid base?

  • 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


What is the renal handling of A/B?

  • 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


What are % of reabsorption of bicarb in diff segments?

85% proximal tubule

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


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

  • 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


What happens to HCO3 molecule in lumen?

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)


What occurs in Type A intercalated cells in distal tubule?

  • 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


Acid secretion is ____ process

active process


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

  • 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


What happens if we have too much base?

We excrete bicarbonate via type B intercalated cells


What happens if we have too much acid?

  • 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


What are titratable acids?

All the buffers that H can potentially bind to besides bicarb

  • Only a finite amount of titratable acids


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

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


What is glutamine?

  • 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


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

Reabsorbs bicard

produces ammonium


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

Reabsorb Bicarb in ascending loop


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

Reabsorbs bicarb

secretes bicarb


What is equation for net acid excretion?

TA + NH4- HCO3

TA + NH4= excreted acids

Tells HCO3 gain/loss from body


What happens to NH4 and TA during acid load

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


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

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


Acidosis can result from either?

gain of acid or loss of bicarb


What causes acid gain? Base loss?

  • 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


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

  • 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


What situations in body would lead to alkalosis?

  • 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