Renal: Diuresis Flashcards
what are diuretics ?
drugs that increase urinary volume
what are the targets for diuretics?
Na entering pathways
How does carbonic anhydrase (CA) inhibitors cause diuresis?
inhibits apical proton secretion and Na entrance and basolateral HCO3 reabsorption
CA inhibitors cause an increase in Na+, HCO3–, and water in the lumen
example of CA inhibitors
Acetozolamide (Diamox)
what is a problem with CA inhibitors?
decrease K
A high Na load increases Na reabsorption in the CCD. This then increases K secretion via basolateral Na,K-ATPase and luminal K channels (“Sacrifice K to retain Na”)
what is true of CA inhibitors ?
weak diuretics
act in proximal tubule
decrease Na, H2O, & HCO3 absorption
increase K excretion (hypokalemia)
metabolic acidosis (low HCO3 in blood)
where do loop diuretics work?
they block Na-K-Cl cotransporter (NKCC) in the Thick Ascending Loop (TAL)
What is result of loop diuretic?
inhibit Na transport in TAL where 20% of Na is reabsorbed.
osmotic gradient fails in the medulla, can’t concentrate the urine (conserve H2O) so H2O is excreted with urine
what are examples of loop diuretic?
furosemide (lasix)
bumetanide
why do loop diuretics cause metabolic alkalosis?
Loop diuretics make K secretion so substantial that the luminal K begins to stimulate H/K-ATPase in nearby intercalated cells. These cells are type A intercalated cells that secrete acid (A stands for acid secretion). As H+ is secreted, urine becomes acidic. H+ is produced from CO2 hydration, which also produces HCO3–. Thus, whenever H+ is secreted, HCO3– is reabsorbed to the blood. The outcome is an increase in plasma HCO3–,
what is true of loop diuretics?
strong diuretic
increase H2O, Na, K, and H excrection
cause hypokalemia, metabolic alkalosis, volume depletion
how do thiazide diuretics work?
increases Ca reabsorption while inhibiting Na reabsorption
What is true of thiazide diuretics?
weak diuretics
act on NCC (Na-Cl cotransporter) in DT
increases Na, K, H, and H2O excretion
increase Ca reabsorption
can cause hypokalemia, metabolic alkalosis, hypercalcemia
K- sparing diuretics act on which part of the nephron?
directly on the principle cells of the cortical collecting duct (CCD) by inhibiting epithelial Na channels and inhibit aldosterone
what is true of K-sparing diuretics?
weak diuretics
decrease Na reabsorption
decrease K secretion
Antagonize (blocks) aldosterone
