The Role of the Kidneys in Acid/Base Balance Flashcards
What is the main acid/base buffer?
Bicarbonate
What is the neat “twist” of the bicarbonate system?
It converts nonvolatile acid to a gaseous form the can be eliminated rather than just buffered.
Basically, it converts H+ to CO2, allowing it to be eliminated through respiration.
What happens to the acid anions that produced the H+ in the first place?
They are small, so they are excreted.
Where does new bicarbonate come from?
It gets made in the tubular cells, because getting it from our diet doesn’t work well.
What energy does NHE use to transport it’s cargo?
NHE uses the sodium gradient to exchange sodium for hydrogen.
What does NBC do?
NBC is a cotransporter with sodium and bicarbonate, both out of the cell.
What does carbonic anhydrase do?
It catalyzes the reaction between bicarbonate and CO2/HCO3
Where does the new bicarbonate go after synthesis in a tubular cell?
The new bicarbonate is moved into the ECF through a bicarbonate/Cl exchanger
Where does the free hydrogen ion go after bicarbonate synthesis in a tubular cell?
The free H+ leaves into the the urine through a H+ ATP-ase
Why isn’t the urine super acidic, with all that H+ being pumped into it?
There are urinary buffers.
- HPO4 from bones is a buffer, and can be excreted. Titratable Acid is another name.
- Ammonia trapping is the second, more controllable mechanism.
Where does NH3 come from?
Glutamine is broken down (via glutaminase) and generates an ammonia.
Tell me about the levels of glutaminase and how they vary.
They can change over the course of several days to compensate for chronic acidosis.
No synthesis is possible until reabsorption of _____ is complete.
Bicarbonate
Hydrogen ion secretion rate depends on ____ and the number of _____
pCO2; the secretion mechanisms.
