Flashcards in Renal Regulation Acid Base Balance Deck (60):
How do we intake acids? get rid of them ?
1. In our diet and metabolism
2. loss of acids and bases in the GI tract + urine (depending on the needs of the body )
What do we ingest more in our diet ? Acids or Bases?Why?
2. Processed or fatty foods
We usually rake in more than we need in the body- so we will most likely excrete acids.
What is a buffer?
Molecule that helps maintain normal pH levels when there are addition of acids or bases.
Main buffer in our body fluids?
Main buffer?Where? Equation?Depends on what?
CO2 and HCO3 buffer system; ECF
- REVERSIBLE Equation !
Depends on Concentration of substate and enzymes.
CO2 + H2O H2CO3 HCO3- + H+
What buffers ICF fluids?
More buffering is done here because we have more fluid in ICF vs. ECF.
3. K+/H+ exchanger
What buffer system is our first line of defense? Why?
ECF - because that is where the fluid goes first (ingestion of acids)
How do we move fluids from ECF to ICF?
K+/H+ exchanger- these are transporters located on our cells.
A K+ will be exchanged for H+ if there is more H+ OUTSIDE the cell.
- cause H+ to enter cell and cause ACIDOSIS
when there is too much H+ in cell- it will move out of the cell and K will move into the cell.
What system is CO2 dependent on? Examples?
The Respiratory system
1. Holding breath causes an increase in CO2 (acid buildup)--> decreases pH
2. Hyperventilation causes decreased CO2 levels (alkalosis)--> increases pH
What happens to HCO3- in the body?
1. Normally reabsorbed (about 100%)
2. Freely filtered
3. Normal levels = 24 mEq/L (24 mmol/L)
4. 4320 mmol/L = FL of Bicarb if normal daily GFR is 180l/day.
What 2 places in the nephron do we see acid base balance ?
1. Proximal Tubule
2. Distal Tubule
What happens in the PT?
1. Reabsorption of HCO3-
2. If necessary- we will secrete acids (in the form of NH4+)
What happens in the DT?
1. May finish reabsorbing
2. Excrete bases (in the form of HCO3-)
3. Excrete acids (in the form of H+)
Where does reabsorption of HCO3- take place? What percentage?
1. PT- 85 %
2. Thick Ascending Limb- 10%
3. DT and Collecting Duct- 5 %
How do we reabsorb HCO3- in PT?
A different HCO3 molecule from the apical membrane than in the blood
NO NET CHANGE in HCO3- in blood
CO2 + H2O forms what in the cell?
H2CO3 (Carbonic acid)
H2CO3 (Carbonic acid) breaks down into what in the cell? With what enzyme?
1. HCO3- and H+
2. Enzyme is Carbonic Anhydrase
When H+ is in the cell, how do we get it into the lumen?
By using the Na+/H+ exchanger (countertransporter) which is on the apical membrane
What hormone increases Na/H transporters located on the apical membrane of the PT?
What happens in the lumen when Na/H pumps H+ into the lumen?
H+ (is secreted and) binds with a HCO3- that has been filtered already.. will then form Carbonic acid--> these will break up into--> CO2 and H2O
What happens to your filtered HCO3- in the lumen?
It is gone - because it binds with secreted H+ to form --> H2CO3--> CO2+ H2O
What happens to the HCO3- molecule made inside the cell?
It will get pumped across the BLM by a Na/ HCO3 symporter -- now we get a new HCO3- molecule into the blood.
What are 2 transporters used on the BLM of proximal Tubule for Acid base regulation?
1. Na/ HCO3 symporter
2. Cl/ HCO3 antiporter
Explain Type a - Distal Tubule Mechanism for Acid base balance.
1.Begins in the cell with CO2 and H2O
2. Carbonic anhydrase converts H2CO3 to HCO3 and H+
3. Apical membrane transporters are different - need energy (primary active transport)!! - so we use K+/H+ ATPase OR H+ ATPase pump.
4. The pumped out H+ will bind with filtered HCO3 to form H2CO3--> CO2 and H2O.
5. The HCO3 made in the cell will be pumped out using HCO3/Cl exchanger on the BLM
What transporters do we use on the Apical membrane for the PT? BLM?
1. Na/H exchanger for Apical membrane
BLM have both
2. Na/HCO3 symporter
3. Cl/HCO3 antiporter
What transporters do we use on the Apical membrane for the DT(Intercalated cells- type A- alpha)? BLM?
BOTH ON APICAL M require energy! (Primary active transport)
1. K+/H+ ATPase pump
2. H+ ATPase pump
3. ONLY have HCO3/Cl exchanger on BLM
What is the difference between alpha and beta intercalated cells of the Distal tubule? when will we have each one?
Same exact transporters but they are located on opposite membranes.
Alpha cells- reabsorption of HCO3- when we are in need of it
Beta cells- secretion of HCO3- high HCO3(BASE LOAD)/ low acids (ALKALOSIS)
How do we get rid of too much acid?
1.High intake of acids
2. Acids enter ECF (no pH change because of our buffer system- HCO3)
3. HCO3 decreases in ECF because it buffers with H+
4. We need to bring HCO3 back up - make more HCO3
5. Kidneys need to make new HCO3
What 2 ways do we make new HCO3?
1. Secrete ions and combine it with another filtered ion (that is not HCO3-)
2. Excrete NH4+
Explain how we make new HCO3 and get rid of acid.
1.If we have no more filtered HCO3
2. H+ can combine with other buffers in our blood ( Titratable acids,PO43-, etc)
3. no pH change
4. new HCO3 we made in cell can be pumped out with HCO3/Cl exchanger
5. We made a new HCO3 in the blood
When we measure titratable acids in the urine (excreted) what are we really measuring?
The number of new HCO3 molecules created in the blood.
What is important to note about titratable acids?
There is a finite amount.
Only a certain number we can do because it depends on the number of titratable acids that are filtered.
*********What happens when there is not a titratabale acid for the secreted H+ to bind to ?
******Through the creation of NH4+
****Where are titratable acids created?
******1. In the distal tubule
*****Where is NH4+ excreted?
*****in the proximal tubule
What is the basis for creating NH4+ ?
What is glutamine? How is it taken up?How long?
1. An AA
2. Taken up by the PROXIMAL Tubule
3. Glutamine is converted to HCO3 and NH4+ molecule after many enzymatic reactions.
4. HCO3- is moved into blood (NEW)
5. NH4+ is secreted into lumen
6. THIS PROCESS IS A DELAY!! -- great and unlimited way to get rid of acids-- but it takes time
What acid-base function occur in the PT?
1. Reabsorb bicarb
2. produce ammonium (if there is too much acid)
What acid-base function occur in the Ascending Loop of Henle
1. reabsorb bicarb
What acid-base function occur in the DT?
1. Reabsorb bicarb
2. secrete bicarb
What is Net Acid Excretion ?
Tells how much of a role the kidneys played in acid excretion- by
1. Titratable acids excreted
2. NH4+ made
& both of these ways we make a new Bicarb molecule
What is the equation for Net Acid Excretion?
NAE= (TA + NH4+) - HCO3-
What is our NAE when we have excess acid?Excess base? 3 factors for each.
1. Excess acid
a. HUGE AMOUNT of NH4
b. NO HCO3
c. High NAE
2. Excess base
a. Small amount of NH4 excreted- because it is delayed process
b. NO titratable acids- you want to keep them
c. NEgative NAE
What are the 2 main causes of Acidosis we see in the body?
1. Gain of acids
2. Loss of base
How do we have an acid gain?
1. Decreased respiration (hypoventilation?)- drugs, airway obstruction, emphysema, chronic bronchitis
2. Ketoacids- used as a fuel source when others aren't available- but they are acids! (Seen in Diabetes)
3. Renal failure- acids levels can rise in the body if they are not excreted by the kidneys
How do we have base loss?
1. Diarrhea- common cause of acidosis
Why is the anion gap (AG) important?What is it used for?
When we have a patient in the state of acidosis, the anion gap helps us determine whether it is due to
1. Acid gain
2. Base loss
How do we calculate Anion Gap ?
AG= Na - (Cl + HCO3)
major cation minus major anions
If we have a normal Anion gap during acidosis-- tells us...
We have a base loss-- When we lose bicarb, Cl actually replaces it so the anion gap stays normal even though you have less base/ bicarb!
What is the anion gap? Normal value?
1.The space between Na and Cl
2. 8 - 12
What are acids labeled as in terms of the Anion Gap?
When we have an acid it the body- they are ANIONS so they go in the unmeasured anon group-- which will increase the Anion Gap. AG grows the more acid in the body.
How do we lose acid?
1. Vomiting- because there's a lot of it in the stomach- stomach acids
How do we gain bicarb?
1. Bicarb overdose- TUMS (Anti-acids)
2. Chronic diuretic usage-
chronic inflammation of kidney
increased Nitrogen in blood
What is a normal respiration rate?
What is marked cyanosis?
What is a loud strider?
Loud whistle sound heard while breathing
When we have alkalosis, where do we move K+ ions?
Into the cell