renal part 4 Flashcards
how do Osmotic diuretics work?
retain water by increasing osmotic pressure
where in the nephron do osmotic diuretics work?
Proximal Tubule
&
descending Loop of Henle
how do carbonic anhydrase inhibitors work?
reduce Na+ reabsorption
the __________ is the major site of action for carbonic anhydrase inhibitors
proximal tubule
how do loop diuretics work?
inhibit Na+ reabsorption via the Na+ K+ 2Cl- symporter
where do loop diuretics primarily work on?
act in Thick Ascending Loop
________ diuretics block Na+Cl- symporter
thiazide diuretics
what part of the nephron do thiazide diuretics work on?
the early distal tubule
K+ sparing diuretics work by doing what?
inhibit sodium reabsorption AND potassium secretion
what part of the nephron do K+ sparing diuretics effect?
actin in:
late Distal Tubule
Cortical Collecting Duct
what are the 2 classes of potassium-sparing diuretics?
- aldosterone antagonists
2. ENaC blockers
what are Aquaretics?
ADH receptor antagonists
_______ diuretics act where tubule is freely permeable to water
osmotic
osmotic diuretics work by impairing __________ reabsorption
Na+
what % of filtered Na+ is excreted when taking an osmotic diuretic?
10% of filtered Na+ is excreted
_________ is also not reabsorbed when taking an osmotic diuretic, due to the lack of solvent drag
Calcium
Ca2+
what are 2 examples of osmotic diuretics?
1) mannitol
2) glucose
what is the effect of inhibiting Carbonic anhydrase in the proximal tubule?
reduces the H+ available for the Na+/H+ antiporter
why are Carbonic anhydrase inhibitors most effective in the proximal tubule?
its where about 1/3 of Na+ reabsorption occurs
why are Carbonic anhydrase inhibitors not particularly effective?
downstream segments will increase Na+ reabsorption when tubular Na+ increases
____________ diuretics Inhibit Na+K+2Cl- symporters in the thick ascending limb
loop diuretics
what is the effect of inhibiting Na+K+2Cl- symporters in the thick ascending limb?
- inhibits Na+ reabsorption
- urine leaving loop is not dilute
why does the loop diuretic’s ability to stop dilution of urine make it so effective?
no osmotic gradient established in the medulla interstitium so water not reabsorbed along collecting duct
Loop diuretics can increase Na+ excretion to as much as _____% of filtered load
25%
_______ diuretics block Na+Cl- transporter in the distal tubule
thiazide
what percentage of Na+ is excreted when a thiazide diuretic is taken?
5-20% of the filtered Na+ is excreted
how do aldosterone antagonists work?
block aldosterone’s ability to increase Na+ transporters in principal cells of the collecting duct & distal tubule
aldosterone antagonists must get inside _____ cells to block aldosterone receptors
tubular
How do ENaC blockers work?
block Na+ reabsorption across the apical membrane of the collecting duct & distal tubule
________ (a ENaC blocker) is secreted into the proximal tubule
amiloride
why does the continued use of diuretics lessen their effectiveness?
diuretics decrease ECV, which means compensatory mechanisms get activated
diuretics will cause the decreased release of ______________
natriuretic peptides
what occurs in the juxtaglomerular apparatus when a diuretic is taken?
- secretes renin
- causes increased angiotensin 2 & aldosterone
- end result: decreased Na+ excretion
why do many diuretics also increase the excretion of K+?
due to:
- increased rate of flow of tubular fluid which stimulates K+ secretion
- Reduced ECV which stimulates aldosterone production
________ balance is affected by all diuretics
Acid-base
metabolic acidosis is caused by what class of diuretics?
CA inhibitors
and
K+ sparing diuretics
metabolic alkalosis is caused by which classes of diuretics?
Loop and thiazide diuretics
why would K+ sparing diuretics cause metabolic acidosis ?
because H+ secretion in distal tubule and cortical collecting duct is inhibited
Except for the K+ sparing diuretics, all other diuretics alter _______ excretion
calcium (Ca2+)
which 2 diuretics act in the proximal tubule and reduce reabsorption of calcium in this segment (so excretion is increased)?
Osmotic and CA inhibitors
Loop diuretics increase calcium excretion by what mechanism?
by affecting the transepithelial voltage
its normally the driving force for paracellular transport of calcium
_________ diuretics stimulate calcium reabsorption in the distal tubule and thus reduce excretion
thiazide
the distal tubule reabsorbs ____% of filtered calcium via active transport
9%
Patients with chronic renal failure are almost always diagnosed with ________
anemia
why does chronic renal failure cause anemia?
due inadequate secretion of erythropoietin (EPO) and loss of erythrocytes.
EPO produced by ________________ in renal cortex
interstitial fibroblasts
when is EPO production stimulated?
when PO2 is low
what does EPO stimulate?
EPO stimulates differentiation of erythrocyte progenitor cells in the bone marrow
EPO production is controlled at the ____________ level
transcriptional
T/F: hypoxia-inducible factors 1 and 2 (HIF-1 and HIF-2) are produced when there is a drop in PO2
FALSE
they are continually produced
why do HIF-1 and HIF-2 not continually act as transcription factors?
they are targeted for degradation when O2 normal
