Renal Acid/Bicarbonate Transport

Question 1

what is the role of the kidney in acid/base balance?

Answer 1

excrete non-volatile acids

reabsorb filtered bicarbonate

Question 2

what happens as a renal of renal acid secretion?

Answer 2

• bicarbonate reabsorption
• formation of titratable acid
• ammonium excertion
• urinary acidification

Question 3

how do hydrogen ion ATPases work?

Answer 3

carbonic anhydrase makes HCO3- with water and CO2
H is released into lumen
HCO3- is released into blood

Question 4

what are the 3 mechanisms of bicarbonate reabsorption in the proximal tubule?

Answer 4

carbonic anhydrase
titratable acid formation
ammonium excretion

Question 5

what are examples of titratable acids? which is most important?

Answer 5

phosphate**
urate
creatinine
beta hydroxybuterate

Question 6

where does ammonia come from?

Answer 6

glutamine to glutamate

Question 7

what is most H secretion used for?

Answer 7

bicarbonate reabsorption

Question 8

what happens to urine pH if H is used for bicarbonate reabsorption, titratable acid formation, and ammonium excretion?

Answer 8

stays constant

any extra H that aren’t used for those things lower the pH of the urine

Question 9

what happens during renal failure?

Answer 9

renal osteodystrophy- bone loss
plasma phosphate increases, causing plasma Ca to precipitate
body things Ca is low, so more PTH is released which signals for bone resorption to get more calcium

Question 10

what does PTH do?

Answer 10

increases Ca reabsorption

decreases phosphate reabsorption

Question 11

what is the SLGT2 transporter? what are its characteristics?

Answer 11

glucose transporter
high Vmax
low glucose affinity
coupled to 1 Na
can be inhibited by drugs

Question 12

what is the SLGT1 transporter? what are its characteristics?

Answer 12

glucose transporter
low Vmax
high glucose affinity
coupled to 2 Na

Question 13

what is Faconi Syndrome?

Answer 13

proximal tubule disease where glucose, AA, phosphates, and bicarbonate are lost due to impaired reabsorption
symptoms: polyuria–>hypokalemia, polydipsia, dehydration, acidosis
common feature of different forms: decreased ATP available for metabolic processes (transport)

Question 14

how does organic anion secretion in the late proximal tubule work?

Answer 14

basolateral- tertiary active transport: Na/K ATPase generates Na gradient that is used to move alpha ketogluterate in which creates a gradient of alpha ketogluterate that is used to move organic abios in via OAT

apical: anion exchanger

Question 15

what organic anions are secreted?

Answer 15

bile salts
oxalate
prostaglandins
PAH
other drugs

Question 16

how does organic cation secretion in late proximal tubule work?

Answer 16

basolateral- facilitated diffusion via OCT

apical- cation/H exchanger

Question 17

what organic cations are secreted?

Answer 17

creatinine
neurotransmitters
drugs

Question 18

what is a problem with using creatinine as a GFR marker?

Answer 18

secreted! but plasma measurements are over estimates, so it evens out
if secretion is impaired, it will look like GFR is decreased when it really isn’t

Question 19

what is gout? how is it treated?

Answer 19

uric acid precipitation in joints and tendons
causes inflammation
drugs:
allopurinol- inhibits uric acid synthesis
probenecid- blocks reabsorption and increases excretion

Question 20

what happens to albumin once inside a tubular cell?

Answer 20

2 options:

• released on basolateral side
• vesicle fuses with a lysosome and the protein is degraded–>amino acids released

Question 21

what is a little protinuria a sign of?

Answer 21

tubular damage

Question 22

what is a lot of protinuria a sign of?

Answer 22

glomerular damage