Muster - Loop of Henle, Distal Tubule & Cortical Collecting Duct

Question 1

what type of cancer is known for causing a proximal tubular dysfuction

Answer 1

Multiple Myeloma

Question 2

what is one classic finding (classical diagnostic tool) in someone with proximal tubule dysfunction

Answer 2

spilling of bicarbonate into the urine until it hits an equilibrium

then if you give them bicarb, it throws off the equilibrium and the pH in the urine starts to rise

can also look for elevated urine glucose in a person with normal blood glucose, can also look for AAs

Question 3

Ingestion of this can cause proximal tubule dysfuciton

Answer 3

lead

Question 4

what is the best equation for estimating creatinine clearance

Answer 4

Cockcroft-Gault

Question 5

orthostatic hypotension is a sign of what

Answer 5

volume depletion

Question 6

key function of the ascending loop of henle

Answer 6

reabsorbs sodium without resorbing water

Question 7

what part of the renal tubule is ONLY permeable to water

Answer 7

descending limb

so the osmolality is greatest in the lowest part of the medullary space at around 1400mOms

Question 8

cells in the ascending limb look like

Answer 8

big and simple cuboidal

Question 9

part of the renal tubule that is not permeable to water

Answer 9

ascending limb

Question 10

where are the NKCC pumps in the renal tubule

what ion is moving down its EC gradient

Answer 10

lumen side in the cells of the ascending limb

sodium is moving down its electrochemical gradient

Question 11

about a third of the sodium that is reabsorbed in the ascending limb moves through the _____

how

Answer 11

pericellular space

its because the Cl- attracts it there (Cl- pumped over via the NKCC pump)

Question 12

bartter syndrome

Answer 12

nonfunctional NKCC pump (lisinopril blocks this)

mental retardation
volume depletion
hypokalemia
metabolic alkalosis
hypercalcURIA

Question 13

where are the NaCl channels in the renal tubule

Answer 13

in the distal tubule (in the cortex)

Question 14

Gitleman syndrome

Answer 14

genetic mutation in the NaCl transporter (HCTZ, chlortalidone block this)

normal BP
metabolic alkalosis
hypocalcURIA
hypomagnesemia
hyopkalemia

Question 15

what is a potassium sparing diuretic

two classes and two examples from each

Answer 15

CLASSICLY:
epithelial sodium channel (ENac) blockers:
Amiloride
Triamterene

or

an aldosterone antagonist (don’t work on just ENac):
Spironolactone
Eplerenone

K STAys
Spironolactone, Triamterine, Amiloride

Question 16

what can happen after you are taken off a diuretic

Answer 16

when you are on the diuretic, your kidney recognizes it as a drop in volume.

When taken off the diuretic the kidney freaks out and takes up even more sodium than you got them off of with your diuretic.

AKA the pendulum swings back too far

Question 17

What is the best time to give a diuretic

Answer 17

after a bid salt meal.

if their diuretic wears off just before they eat a lot of salt, the rebound effect will cause an even greater retention of sodium

Question 18

where is the only place in the kidney that you can have variable and controllable sodium reabsorption

Answer 18

collecting tube

Question 19

epithelial sodium channel

faces what side of cell - lumen or vessel

(ENac)

Answer 19

lumen

Question 20

Renal outer medularry potassium channel

ROMK

Answer 20

just allows potassium to flow back into the lumen of the renal tubule (as the K concentration increases in the tubule cell from the activity of the Na/K antiporter

Question 21

fixed amount of sodium that we resorb

Answer 21

95%

(can only control 5% of your filtered load)

you can maximally get rid of about 5% (50g) of this per day, 95% is always absorbed

Question 22

filtered load equation and normal value for sodium

Answer 22

GFR * [Na]plasma

around 25,000mM/day. (1Kg/day)

1g=25mM

Question 23

juxtaglomerular cells release what

Answer 23

renin

they are in the afferent arteriole

Question 24

why does the distal tubule come back and run next to the afferent arteriole

Answer 24

so that the juxtaglomerular cells can detect:

distal flow rate
Na and Cl delivery

so that they juxtaglomerular cells can tell the distal tubule if they are receiving less stretching. this causes production of renin

Question 25

where does aldosterone cause resorption of sodium in the renal tubule

how does it do it mechanisticly

Answer 25

in the collecting tubule

stimulated by low sodium or high potassium

aldosterone binds steroid response elements, causing an increase in the transcription, translation, and insertion of the Na/K transporter, and the ENac and ROMK channels

Question 26

what happens if you have an upregulation of ENac

Answer 26

going to get more sodium absorption

called “little’s syndrome”

present with salt sensitive hypertension

Question 27

type I pseudo hypoaldosteronism

Answer 27

get a loss of ENac function

you have enough aldosterone, it just doesn’t work on ENac function

get: sodium wasting, fluid wasting