Renal: Acid Base balance Flashcards
(30 cards)
how do most proteins interact with H+
serve as buffers attenuate pH changes without altering total body pH
how do H+ ions come about in the body?
metabolically produced
consumed by food, drugs, etc…
How do the lungs impact H+ ?
add or remove H+ by adding/removing CO2 via ventilation
What other organs regulate H+ ?
kidney
GI tract
what pathologies alter H+ levels?
vomitting – loss of H+ (higher pH = alkalosis)
diarrhea — gain of H+ (lowers pH = acidosis)
what is the importance of H2CO3 (carbonic acid)?
it’s an intermediate that can increase or decrease the pH.
why is CO2/HCO3 important?
important buffer that can maintain H+ level by simply breathing
how much HCO3 is filtered by the body?
4.3 mol/day
GFR x [HCO3 level]
Equivalence of bicarbonate loss and acid gain (and vice versa): formula
CO2 + H2O H+ + HCO3-
in regards to HCO3, how is neutrality accomplished?
all bicarb (HCO3) must be reabsorbed
in regards to HCO3, how is alkalemia (high pH) corrected?
HCO3 must be secreted
in regards to HCO3, how is acidemia (low pH) corrected?
HCO3 must be produced
what enzyme accelerates the production of HCO3?
carbonic anhydrase (H2CO3)
How does reabsorption of HCO3 in the PT occur?
filtered HCO3– first interacts with H+, and makes CO2. CO2 is neutral and enters PT cells. Intracellular CO2 is then hydrated and produces H+ and HCO3–. H+ is secreted to the lumen via NHE, while HCO3 is reabsorbed. Mechanistically, it is H+ and CO2 that are moving through the apical membrane, but the overall result is HCO3– reabsorption.
NOTE: Mechanistically, it is H+ and CO2 that are moving through the apical membrane, but the overall result is HCO3- reabsorption.
what ion impacts HCO3 reabsorption in the TAL?
Cl
if HCO3 needed to be added to the blood in the distal portions of the nephron, how would this occur?
HCO3 is made from CO2 hydration in type A intercalated cells
–new HCO3 to blood and new H+ to tubule lumen
what is the other type of intercalated cell? what is it’s function?
a. type b intercalated
b. secrete HCO3 into lumen and absorb H+. into blood (opposite of type a)
what are considered titratable acids?
phosphates and sulfates (by H+ secrection from intercalated cells in CD)
if phoshate can only titrate 40 mmol/day of acid out of 50 -100 mMol/day (net acid production). What does the rest?
ammonia
NH3
how is nitrogen metabolized in the liver?
NH4 associates with HCO3 and makes either urea or glutamine
how is nitrogen metabolized in the kidney?
Urea is excreted, while glutamine is metabolized to produce NH4+ and HCO3- in the PT
NH4+ is then excreted, while HCO3- and glucose are returned to the body
what regulates nitrogen becoming urea or glutamine?
In acidosis more NH4+ is incorporated into glutamine
In alkalosis more NH4+ is incorporated into urea
in acid/base regulation in the kidney, what happens if plasma is acidic?
(PT/TAL) Secrete H+ —-Save all HCO3
(CD) Secrete H+ by intercalated A cells
Excrete H+ —- as NH4+ and as H2PO4-
Thus, urinary pH is low
(lowest attainable pH = 4.4)
in acid/base regulation in the kidney, what happens if plasma is alkaline?
(PT/TAL) Retain some H+ — Do not save all HCO3
(CD) Secrete HCO3- by intercalated B cells
Turn nitrogen into urea (rather than into NH4+)
Excrete HCO3-
Thus, urinary pH is high (> 7.4)
