Unit 2, L20 Acid Base 2 Flashcards
Define NEAP
Net Endogenous Acid Production, and it is an equivalent loss of HCO3 from the body that must be replaced
For acid base balance to be maintained
Acid must be excreted from the body at a rate equivalent to its addition
What is the amount of nonvolatile acids that is added to the body each day for a meat-containing diet, normal metabolism, and fecal HCO3 loss?
50-100 mEq/day for most adults
How are nonvolatile acids neutralized by bicarb?
Nonvolatile acids are immediately neutralized by bicarb in the ECF
To maintain acid-base balance, the kidneys must do what?
The kidneys must replenish the bicarb lost by neutralization of nonvolatile acids, a process called Renal Net Acid Excretion (RNAE)
Which is regulated, NEAP or RNAE?
RNAE, NEAP is not regulated
What will happen when the kidneys regulate RNAE
1) Replenish the HCO3 (new HCO3) lost by neutralization of nonvolatile acid
2) Kidneys must prevent loss of HCO3 in urine
How much does the PT reabsorb of bicarb
80%
How much does the TAL reabsorb for bicarb
10%
What is the excretion of bicarb?
0%
How much bicarb do we need each day?
50-100 mEq
How much H is secreted and what happens to it?
Nephrons secrete out about 4400 mEq and most of it will reabsorb the filtered load of bicarb
What is the predominant pathway for H secretion in the PT
NHE3 transporter, it is an Na/H exhanger, sends Na in and H out on the apical membrane q
What are the two different isoforms of CA and how do they function
1) CA-IV is present on the brush boarder, so the CO2 and H2O formed readily cross the luminal membrane and enter the cell
2) Ca-II is inside the cell, and this is where H and bicarb are produced
HCO3 is reabsorbed by two mechanisms in the PT, what are they
1) Na-HCO3 cotransporter, also called NBC1
2) Cl-HCO3 exchanger
In the PT, is there increased, decreased, or net reabsorption of Na and HCO3?
Net reabsorption
In the DT, bicarb is being reabsorbed by what transporter
AE1, moves bicarb out towards the blood and Cl into the cell
In the PT, is there H secretion?
No
In the DT, is there H secretion?
Yes, we have secretion from the alpha intercalated cells
In the distal tubule, for each H that is being secreted, what is happening with bicarb
For each H that is being excreted as titratable acid, one new HCO3- is being synthesized and reabsorbed
PT vs DT in terms of H secretion and bicarb
PT: No H acid secretion, and reabsorption of bicarb
DT: H excreted, bicarb synthesis, and reabsorption of bicarb