Renal Control of Acid-Base Balance

Question 1

What is an example of an volatile acid?

Answer 1

CO2

Question 2

What is an example of fixed acids?

Answer 2

Sulfuric acid, phosphoric acids

Question 3

what are some metabolic sources of H+

Answer 3

1. Oxidative metabolism (CO2+H20) –> H2CO3 –> H + HCO3
2. Glycolysis: lactic acid
3. Incomplete oxidation of fatty acid: ketone acids
4. Protein, nucleic acid, phospholipid metabolism: sulfuric, phosphoric, hyrocholric acids

Question 4

What are the 3 lines of defense against pH changes

Answer 4

1. Chemical buffer system
2. Respiration
3. Kidneys

Question 5

What is an example primary buffer system in our body?

Answer 5

Carbonic acid/bicarbonate

Question 6

What makes the carbonic acid / bicarbonate a powerful buffer system?

Answer 6

It’s an open system in that it’s products can be eliminated via two routes/systems (lungs/kidney). One can compensate for the other.

Question 7

How does the kidney respond to excess base?

Answer 7

1. Incomplete reabsorption of filtered HCO3
2. decreased H secretion
3. Secretion of HCO in collecting duct by the beta intercalated cells.

Question 8

Free urinary H is about 40 umol/L at a pH 4.5 meaning that the body would need 2500L to excrete 100 mEq of H, which is not physiologically possible. How is problem accomplished?

Answer 8

Most H are excreted in combination with urinary buffers which include titratable acids, and ammonia.

Question 9

What is a titrable acid and give an example

Answer 9

Conjugate bases of metabolic acids. Example: phosphate, creatinine, urate.

Question 10

How do you calculate Total renal H excretion?

Answer 10

H = urinary excretion of titratable acid + ammonium - HCO3

Question 11

what is urine acidified the most and how?

Answer 11

DCT and Collecting duct done by the alpha and beta intercalated cells.

Question 12

The alpha intercalated cells in the DCT and CD are under directly stimulation by what? and what is the effect?

Answer 12

Directly stimulated by alodsterone and secretes H.

Question 13

The beta intercalated cells of the DCT and CT are responsible for what in maintaining acid-base balance.

Answer 13

eliminate excess base. Takes in Cl and secretes bicarb

Question 14

Where does acidification of urine began and what causes this acidification?

Answer 14

in the PCT. Due to H excretion and binding to ammonia to form ammonium.

Question 15

Can HCO reabsorption be saturable?

Answer 15

Yes.

Question 16

What is the most important buffer that’s converted to titratable acid that which can help excretion of H?

Answer 16

HPO4

Question 17

What are some factors that control renal H secretion?

Answer 17

1. IC pH. Decreased IC pH, H is secreted
2. Plasma PCO2: when plasma PCO is increased, H is excreted
3. Carbonic anhydrase activity. with this enzyme inhibited –> metabolic acidosis since you can’t reabsorb bicarb. H is excreted.
4. Na reabsorption
5. EC [k] –> secrete H
6. Aldosterone. work directly with H ATPase and secretes it. and Na/H exchanger which secretes H

Question 18

How does diuretic abuse cause alkelemia?

Answer 18

With excessive use of diuretics you’re contractint ECF and thus contraction, renin section, plasma renin, aldoseterone, All leads to tubular secretion of H leading alkalemia.

Question 19

How does diuretic abuse cause potassium depletion?

Answer 19

As K is depleted, leads to increased reabsorbed of all filtered bicar and contributes to metabolic alkalosis.

Question 20

Give an example of contraction alkalosis.

Answer 20

Diuretic abuse