11/20 Flashcards
Where in the kidney do we secrete the compounds that the body needs to get rid of like organic compound transporters?
in the PCT
Why does the PCT have a really high metabolic rate?
It needs energy to reabsorb and secrete everything that it does
Which part of the loop of Henle do we have 20% of our water that was originally filtered be reabsorbed?
Thin descending limb
By the time the water that was filtered at the glomerular capillaries makes it to the end of the thin descending limb of Henle, what percent of it is reabsorbed?
~85%
2/3 + 20% = ~85
the ascending limb of the loop of Henle is relatively ______ to water
impermeable
The regulation of exactly how much water we hold on to happens where in the kidney?
The collecting duct and distal tubule
The Thick Ascending Limb is where we reabsorb what? (vague)
lots of stuff, primarily ions
What percent of the ions or electrolytes that are filtered get reabsorbed in the Thick ascending limb?
25%
2/3 of the ions/electrolytes that are filtered get reabsorbed in the PCT + 25% get reabsorbed in thick ascending limb.
Which cells decide what happens to the rest of it?
principal cells in the last part of the tubule
Where are principal cells found?
late part of distal tubule and pretty much all of the collecting duct
Water regulation in the late part of the tubular system is dependent on
How much Vasopressin/ADH floating around
Vasopressin/ADH allows us to
fine tune the amount of water we are reabsorbing
Which two portions of the tubule have a high metabolic rate?
PCT and thick ascending limb
In the distal tubule, which transporter does the heavy lifting in regards to getting Ca++ reabsorbed from the tubular lumen?
Na+/Ca++ exchanger
The secondary pumps are the Ca++ ATPase pumps
The electrochemical gradient that the Na+/Ca++ pump depends on is formed from the
Na+/K+ pump
This keeps Na+ concentrations low in the cell and bc of that Na+ wants to come into the cell from the interstitium
One of the things we can do to make the Na+/Ca++ pump spin faster is to
block Na+ entry from the tubular fluid from entering the cell
How does sodium get into the distal tubule cell?
Though a simple Na+/Cl- pump on the luminal side of the cell, then it is pumped out by the Na+/K+ pump and then brought back into the cell via the Na+/Ca++ exchanger.
If we block the Na+/Cl- pump in the distal tubule with a ________ (drug) then
thiazide diuretic
Then it should speed up the cycling of the Na+/Ca++ exchanger which would increase the amount of Ca++ that gets reabsorbed.
What kidney drug is prescribed for osteoporosis and why?
thiazide diuretic
It speeds up the Na+/Ca++ exchanger which helps them reabsorb more Ca++
if you are on a thiazide diuretic, then which supplement do you have to be mindful of?
Ca++ supplements
Prevention of kidney stones can include ____(drug). why
thiazide diuretics.
Stones are made from crystalized Ca++.
This drug is not good for removing stones that are already formed but can be good for prevention
When you think of principal cells think of
Aldosterone
The more aldosterone we have the more ____ we reabsorb
Na+
Aldosterone is a
mineralocorticoid. It helps us manage and maintain our electrolyte balance
What makes aldosterone levels rise?
low blood pressure or low sodium
Having a lot of aldosterone has what effect on K+?
It decreases K+
works by:
aldosterone binding to intracellular aldosterone receptors which speeds up the Na+/K+ pump on the ISF side of the cell. Na+ goes into the ISF and K+ goes into the cell.
We have channels on the tubule side of the cell that is going to allow K+ out into the tubule and Na+ into the cell.
This means we have a bunch of Na+ moving towards the renal ISF (reabsorption) and a bunch of K+ moving towards the tubule (secretion)
Aldosterone (probably) increases the number of K+ channels and (definitely) increases the number of Na+ channels found on the tubule side of the cell. The more channels we have the more/faster the ion movement is going to be.
How does K+ get into the tubule from the tubular cells in the distal tubule?
Through a channel that stays open NOT A PUMP.
Despite this, this process is still called secretion because it is relying on the Na+/K+ pump
Lots of aldosterone = lots of K+ ______ in the distal tubule
secretion
What does the aldosterone do directly in the distal tubule?
- speeds up Na+/K+ pump
- Enhances the number of Na+ channels in the cell wall
- Likely also plays a role in how many open potassium channels we have in the tubule side of the wall as well. (not as well ironed out)
What are the two types of K+ channels that operate in the principal cells?
ROMK (renal outer medullary K+ Channel)
BK (Big K+ channels)
How do the ROMK and BK channels work?
If we don’t need to get rid of a lot of K+ then the channels are sequestered inside the cell, waiting to be needed.
If we need to pick up K+ secretion then the ROMK channels get put in the cell wall to be used as extra pathways for K+ to move out of the cell. This is aldosterone mediated
If we have really high K+ excretion the BK channels also open up. This is aldosterone mediated
Those are in the cell wall all the time, it’s just a matter of if they’re open or closed. If we don’t need them they’re closed and if we have a ton of K+ we need to secrete they open.
POTASSIUM maintenance think
PRINCIPAL cells
What is another name of the Na+ channel that is found on the tubule side of the tubular cell in the Distal tubule?
Epithelial Na+ channel
ENaC
What do Amiloride and Triamterene do?
Block the ENaC pump in the distal tubule which indirectly slows down the K+ secretion by slowing down the Na+/K+ pump. This might be useful if you wanted to hang on to K+.
aldosterone receptor antagonist example:
spironolactone
spironolactone
Blocks the aldosterone receptor in the distal tubule which slows down the Na+/K+ pump which slows down K+ secretion and Na+ reabsorption
What are the K+ sparing diuretics?
Amiloride
Triamterene
spironolactone
A loop diuretic slows down reabsorption where in the kidney?
Thich Ascending Limb in the loop of Henle
Thiazide diuretics work in what part of the kidney?
just upstream of principal cells
Osmotic diuretics reabsorb water in which part of the kidney?
the early parts of the tubule
Anything that reduces NaCl reabsorbed upstream of principal cells have what effect on water reabsorption?
indirectly decreases water reabsorption or increases water leaving the body
K+ wasting diuretic.
Anything that reduces NaCl reabsorption before the principal cells leads to what effect in the later part of the tubule?
Means more will be reabsorbed in the later parts where there are principal cells which would increase K+ secretion
K+ wasting diuretic
Smidt says if you are on a K+ wasting diuretic but you want to conserve K+ then
you might be put on a small dose of a K+ sparing diuretic too to increase volume excretion but limit K+ wasting.
what is the most commonly prescribed diuretic combination?
Triamterene with Hydrochlorothiazide
Where does aldosterone come from?
zona glomerulosa- the most outside part of the adrenal gland
Layers of the adrenal cortex outside to inside:
zona glomerulosa
zona fasciculata
zona reticularis
Medulla
What do the zona fasciculata and zone reticularis produce?
- most of our cortisol (helps us even things out when we are under stress)
and androgens including androstenedione (an anabolic steroid that converts to sex hormones)
a small amount of estrogen from the zona fasciculata specifically.
If you have a crazy on the tumor zona fasciculata you would produce a lot of
estrogen
Where do catecholamines(epi/norepi) come from?
The deep inner part of the adrenal cortex called the Adrenal Medulla.
What is the ratio of epi to norepi that is released at the adrenal gland?
4epi : 1norepi
aldosterone secretion is sensitive to
K+ levels.
High potassium= high aldosterone
Low potassium = low aldosterone
angiotensin II binding to at1 receptors at the zona glomerulosa
What is the enzyme that produces aldosterone? Where in the body is this found?
aldosterone synthase
Found in the zona glomerulosa
aldosterone, cortisol and estrogen are derivatives of
cholesterol
What is the difference in the shape of aldosterone, cortisol and estrogen?
1 chemical modification to differentiate them from each other.
However they all look very similar to cholesterol and each other