Lecture 9 - Secretion mechs and HCO3- regulation

Question 1

In the PCT, _______ is brought into the basolateral side via cotransport with Na+ –> then, Anions enter the Basolateral side in exchange for ________ back into the ECF.

Answer 1

Alphaketoglutarate (alphaKG)

AlphaKG

Question 2

Cations enter the basolateral side of PCT cells via _______ diffusion –> then they exit the Apical side into the lumen via Antiporter that brings _____ INTO the cell from the Lumen.

Answer 2

Facilitated

H+

Question 3

Diuretics act in the lumen of the Nephron. Thus, they need to be ______ in order to get there bc they are not very well ______.

Answer 3

Secreted

Not well Filtered

Question 4

In the Collecting duct, where about 10% of HCO3- is reabsorbed, how do Type A (alpha) intercalated cells reabsorb HCO3-?

How does this differ from Type B intercalated cells?

Answer 4

Type A intercalated cells have V-type K+/H+ antiport ATPase on the APICAL side, which moves H+ into the lumen to combine with lumenal HCO3, forming CO2 —> CO2 diffuses into cell –> reforms HCO3- inside cell –> HCO3- is moved out into the ECF on the Basolateral side via Anion exchange with Cl-.

Type B intercalated cells transport all the same things but in the OPPOSITE direction/side of the cell.

Question 5

When HCO3- in the lumen of the nephron is exhausted, Titrateable acids and ______ can continue to buffer secreted H+. Keep in mind the minimum pH of filtrate in the lumen is _____ –> H+ secretion would stop at this pH.

Answer 5

Ammonia (NH4+)

4.4

Question 6

In the PCT, NH4+ is generated via breakdown of _____ into alpha-ketoglutarate –> this yields 2NH3 that will consume 2H+ to form 2NH4+. Remember that CO2 is the source of H+ in the cells, so as H+ is consumed, CO2 is broken down into _____ and H+. The newly produced _____ can be moved to the ECF to continue buffering the serum.

Answer 6

Glutamate

HCO3-

HCO3-

Question 7

A decrease in plasma pH will have what effect on the transport and subsequent breakdown of Glutamate in PCT cells?

Keep in mind NH4+ formed INSIDE the cell is secreted in exchange for Na+ (via antiporter), but NH3 formed in the cell can diffuse out and combine with H+ in the lumen (thus buffering the filtrate).

Answer 7

Glutamate transport into the cells will increase –> more breakdown produces more NH3 –> consumes more H+ to form NH4+

Question 8

Serum Anion Gap is calculated as:

AG = ?

Normal AG range is ____-____mEq/L

Answer 8

AG = Na - (Cl + HCO3-)

8-12mEq/L

Question 9

Renal Tubular Acidosis is defined as Acidosis ______ (with or without?) kidney failure.

Answer 9

WITHOUT kidney failure

Question 10

________ inhibits Carbonic Anhydrase –> decreases _____ reabsorption –> alkalinize urine –> serum acidosis.

Answer 10

Acetozolomide

HCO3-

Question 11

Thiazides and Furosemide cause H+ secretion into filtrate by:

Activating the _____ system,

Enhancing Na+ delivery to the Collecting tubules which will respond by increasing _____ activity –> more negative lumen –> increase H+ secretion,

and by inducing hypokalemia which the kidney tries to compensate for by increasing H+/K+ exchange (K+ reabsorption increases and H+ secretion increases).

Answer 11

RAAS

ENaC

Question 12

At what bladder volume does the urge to urinate occur?

Answer 12

About 150mL

Question 13

Conversion of 25OH D3 to 1,25diOH D3 (calcitriol) occurs in the Kidney via the enzyme ________ which is stimulated by _____. Remember that 1,25diOH D3 increases Ca++ absorption in the _____.

Answer 13

1-alpha-hydroxylase

PTH

Intestines