Block 4.4 -- Renal Regulation

Question 1

In the early nephron (proximal tubule), kidneys reabsorb bicarbonate and can secrete what two things?

Answer 1

Acids and bases

Question 2

The mechanism of bicarbonate reabsorption involves tubular secretion of what? Is this technically absorption?

Answer 2

Hydrogen ion and no

Question 3

Bicarbonate is filtered and combines with hydrogen ion (carbonic anhydrase mediated) to form water and CO2. This then diffuses into the cell to form what two things (carbonic anhydrase)?

Answer 3

Bicarbonate and H+

Question 4

The overall net result is bicarbonate filtered from blood is replaced by bicarbonate from ‘what’?

Answer 4

Reabsorption

Question 5

Any hydrogen ion that combines with bicarbonate in the lumen does not contribute to urinary excretion of hydrogen. It instead contributes to conservation of what?

Answer 5

Bicarbonate

Question 6

In the distal nephron (collecting ducts), kidneys can secrete two things. In Type A intercalated, it is what? In type B intercalated cells, it is what?

Answer 6

Type A – Protons
Type B – Bicarbonate

Question 7

In the face of addition of base, the kidneys excrete what? Some filtered bicarbonate is excreted in what?

Answer 7

Bicarbonate
Urine

Question 8

Since the addition of acid reduces bicarbonate, the kidney must replace lost bicarbonate generated from CO2 and water, while excreting what?

Answer 8

Hydrogen ion

Question 9

Hydrogen ions are secreted and combined with other what with the acid form being secreted?

Answer 9

Buffers

Question 10

Which extracellular buffer is a synthesized buffer?

Answer 10

Ammonium

Question 11

Which extracellular buffer is a filtered buffer?

Answer 11

Phosphate

Question 12

New bicarbonate is generated where we can’t rely on ‘reabsorption’ of bicarbonate. New bicarbonate in the blood is accompanied by excretion of equivalent amount of buffered what?

Answer 12

Hydrogen

Question 13

In the proximal tubule, ammonium (NH4+) is generated from what? The ammonium is transported into the renal lumen in exchange for sodium by a luminal sodium/ammonium exchanger.

Answer 13

Glutamine

Question 14

The ammonium is excreted with filtered chloride as its anion. This generates new what (via glutamine metabolism) while excreting an acid (ammonium chloride)?

Answer 14

Bicarbonate

Question 15

In the collecting tubule, ammonia (NH3) diffuses into and combines with hydrogen secreted by the H+ATPase. The hydrogen is generated from what two things via carbonic anhydrase?

Answer 15

Carbon dioxide and water

Question 16

Excretion of hydrogen is linked to generation of new what?

Answer 16

Bicarbonate

Question 17

General Rule: For the whole organism, renal handling of what has priority? This normally regulates the balance at expense of H+ or K+.

Answer 17

Na+

Question 18

Provided Na+ balance is satisfied, pH regulation will often occur at the expense of [?]ECF regulation?

Answer 18

K+

Question 19

H+ pumped out of what cells will diminish potential gradients, thus limiting capacity to excrete K+?

Answer 19

Intercalated cells

Question 20

Acidosis stimulates the secretion of H+ and inhibits the secretion of ? ions? Acidosis can also lead to what?

Answer 20

K+, hyperkalemia

Question 21

Hyperkalemia stimulates the secretion of K+ and inhibits secretion of what? It can also lead to acidosis?

Answer 21

H+