6. Renal Acid Base Flashcards
What must pH stay at around 7.4?
AAs have positive and negative charges which can be altered and change protein folding and other protein to protein interactions
Most of the H+ elimination occurs in the lungs while a fixed percent occurs in the kidneys. What happens if there is a change of 0.3 in pH down?
doubles H+ concentration
if pH goes up by 0.3 it will half the H concentration
What is interesting about the pH of urine and what is its range?
4.5 to 8, allow it to concentrate or dilute H+ if needed
What organ regulates retention or elimination of CO2 and therefore H2CO3 concentration in minutes-hours as a cody buffer system?
the lungs
What organ acting as a body buffer system allows bicarbonate reabsorption and regeneration, ammonia formation and phosphate buffering in hours-days?
Kidneys
What organ exchanges calcium, phosphate, and release of carbonate in hours to days to to help with buffering?
Bone
HPO4 has a pK at 6.8 while HCO3 has a pK at 6.1 which are both buffers in the ECF. what occurs at this number?
where this buffer acts as an H+ sponge, sopping up half of the H+ it can absorb
CO2 is transported as CO2 dissolved 7%, 23% HbCO2, and 70% HCO3. How does a majority of the HCO3 get made/transported into the blood?
In the RBC, CO2 and H2o combine to make H2CO3 via CA and then spontaneously breaks down to form H and HCO3, H is then used to bind Hb or is recycled and HCO is transported out of the red blood cell via chloride shift for a Cl- in
Ionoic shifts is another way of buffering (bringing the pH back down or up) the system via Hydrogen being exchanged for Potassium. When there is acidemia (low pH in the ECF), ICF takes in H+ and excretes K+. When there is alkalemia (high pH in the ECF)?
ICF gives H+ to ECF, and takes K+ into ICF
What is the henderson-hasselbalch equation and what is the normal log for pH of 7.4?
pH= 6.1 + log (HCO3-contolled by kidneys)/(H2CO3)
REMEMBER: H2CO3 = 0.3*pCO2 controlled by lungs
when log is equal to 20 = pH 7.4
When log of 1/1 is equal to 0
When you breath fast, theres less CO2 which means less H2CO3 which means less H+ which means higher pH. What happens when you hold your breath?
more CO2, which means more H2CO3, which means more HCO3 and H+ which means more acidic which = lower pH
What is the percentage reabsorbed of bicarbonate in the PCT, TAL, and DC?
PCT = 85%
TAL= 10%
CD= 4.9%
0.1%-1% excreted via urine
By the Na/HATPase, the Na/HCO3 cotransporter and the Cl/HCO3 antiporter in the PCT is where the majority of bicarbonate is reabsorbed. What is the mechanism? (4)
- H+ is secreted into lumen via Na/Hatp
- H+ combines with HCO3, which is then broken down by carbonic anhydrase into CO2 and H20, which freely cross the apical membrane into the cell
- CO2 h2o combine again via CA forming HCO3 and H+ 4. H+ is recycled to go back to lumen and get more HCO3, HCO is transported into the blood against 1 Cl, or 3 HCO3 co transported with 1 Na
The primary factors that regulate increased H secretion and HCO3 reabsorption are a decrease plasma HCO3 (inc pH) and an increase in pressure of CO2. Secondary that regulate Increased H+ secretion and HCO3 reabsorption include? (5)
Increased filtered load of HCO3
Decreased ECF volume
Increased AGTII because Na/Hexchange increases
Increased aldosterone because inc in Na (CD)
Hypokalemia (PCT for all others)
Phosphate buffering of secreted hydrogens helps regenerate lost HCO3 that had been consumed elsewhere when the NaH2PO4 lost an H+ in a less acidic compartment, how?
So the extra H+ is secreted and bound to NaHPO4-, which forms NaH2PO4 which is then secreted in the urine
