Proximal Tubular Dysfunctions and Disorders of Water Balance - Gosmanova

Question 1

What structure does the proximal tubule have that facilitates increased absorption?

Answer 1

microvilli (brush border)

Question 2

Functionally, the PT is divided into three parts. Explain

Answer 2

S1- initial short segment of PCT
S2 - remained PCT and cortical parse recta
S3 - medullary parse recta

Question 3

What are the functions of the proximal tubule?

Answer 3

Reabsorption of filtered water, electrolytes and organic compounds
Secretion of organic compounds and drugs S2/3
Hormonal Function - final pathway in the synthesis active vitamin D

Question 4

What percentage of glucose is reabsorbed in the pt?

Answer 4

100%

Question 5

What percentage of sodium is reabsorbed in pt?

Answer 5

55-65

Question 6

What are the three types of transport ?

Answer 6

primary active
secondary active
passive

Question 7

What drug targets Carbonic anhydrase

Answer 7

acetazolamide

Question 8

What is the function of carbonic anyhydrase

Answer 8

it mediates the conversion of h2c03 into h20 and c02, which can diffuse into the cell.
By inhibiting carbonic anyhydrase, you can cause mild diuresis

Question 9

what transporters does angiotensin II work on?

Answer 9

it activates the H-Na transporter (bringing Na into the cell) and on the HCO3-Na co transporter, pumping both into the basolateral surface

Question 10

Why is the PT highly susceptible to ischemia

Answer 10

it’s depend on atp in the NKA PUMP

Question 11

What are six potential defects in PT function?

Answer 11

defective solute influx
leakage back into the lumen
decreased solute flux into the blood
defective energy generation or transportation
increased backflux across tight junctions
defective transporter recycling

Question 12

PT dysfunction can be due to what and what?

Answer 12

generalized: usually energy generation

genetic or acquired

Question 13

What is hereditary renal glucosuria? and it’s cause

Answer 13

Defect in glucose reabsorption.

Mutation in SGLT2 glucose transporter in PT that absorbs glucose.

Question 14

What is the defect in amino acid reabsorption?and cause?

Answer 14

cystinuira

mutation of brush border transporter responsible for reabsorption of cystine, and ornithinem lysine and arginine

Question 15

what is the common occurence in cystinuria?

Answer 15

kidney stones

Question 16

what are the three common defects in phosphate reabsorption?

Answer 16

x-linked hypophosphatemia
autosomal recessive hypophosphatemic rickets
oncogenic hypophosphatemic osteomalacia

Question 17

What is the most common inherited phosphate wasting disorder? cause

Answer 17

x-linked hypophosphatemia

increased levels of circulating factor FGF-23 that down-regulates activity of phosphate transporter rater than transport protein mutation itself.

Question 18

What is commonly seen in children with x-linked hypophosphatemia?

Answer 18

rickets

adults have osteomalacia

Question 19

t or f hartnup disease is a defect in neutral amino acid transporter in the pt

Answer 19

true

Question 20

what is vitamine d-dependent rickets type 1?

Answer 20

causes by mutation of 1alpha-hydroxylase leading to hypophosphatemia and rickets

Question 21

what are metabolic abnormalities associated with fanconis syndrome?

Answer 21

aminoaciduria
glucosuria
hyperchloremic metabolic acidsos
hypokalemia
uricosuria

Question 22

What are clinical manifestations of fanconis syndrome?

Answer 22

polyuria polydipsia
volume depletion
cardiac arrhythmias
proteinuria
growth retardation
rickets
renal stones and nephrocalcinosis
extra renal organ involvement depending on underlying cause

Question 23

What are inherited causes of fanconi syndrome

Answer 23

cystinosis

Question 24

what are acquired causes of fanconi syndrome

Answer 24

multiple myeloma and tenofovir

Question 25

an osmotic pressure above what will trigger thirst mechanisms?

Answer 25

295

Question 26

What has a greater ability to stimulate adh secretion: change in Posm or decrease in blood volume?

Answer 26

Posm (change by 1%)

BV must decrease by 7% to stimulate ADH secretion

Question 27

What is the mechanism of ADH action in the collecting duct?

Answer 27

AQP2 is the renal collecting duct water channel. It will cause a quick insertion of more aqp2 into the luminal surface. long term will increase the transcription of the aqp2 gene

Question 28

What are two drugs that inh v2rc

Answer 28

conivaptan and tolvaptan

Question 29

what is the cause of hyponatremia?

Answer 29

increased tbw. can have increased or decresaed Na levels as well. but water always predominates

Question 30

what are specific causes of hyponatremia?

Answer 30

renal losses, gi losses, skin, all have volume depletion

normal volume status - SIADH, glucocorticoid deficiency hypothyroidism

volume overload - CHF, kidney failure, cirrhosis, nephrotic syndrome

Question 31

what is central di

Answer 31

lack of adh

Question 32

what is nephrogenic di

Answer 32

can’t respond to adh