DIT Renal 2. Nephron and Diuretics Flashcards
What class of drugs inhibit the Na+/2Cl-/K+ symporter in the thick ascending limb?
Loop diuretics
What determines how much water is reabsorbed in the distal tubules and the collecting ducts?
ADH
What two types of cells compose the collecting duct and the last segment of the distal tubule? What do they do?
Principal cells:
- reabsorb H2O and Na+
- secrete K+
Intercalated cells:
- secrete H+ or HCO3-
- reabsorb K+
What are the two types of intercalated cells?
alpha cells - H+ secreting cells
beta cells - HCO3- secreting cells
What affect does aldosterone have on the intercalated cells and principal cells of the collecting duct?
Intercalated cells - stimulates acid secretion
Principal cells - increase Na+ reabsorption and K+ secretion
What drug antagonizes aldosterone’s action on the principal cells of the collecting duct, thereby promoting Na+ excretion and inhibiting K+ excretion?
Spironolactone
Eplerenone
What are the critical steps involved in excreting dilute urine?
- Dilution of fluid in the TAL as solute is reabsorbed and water remains in lumen (d/t impermeability of H2O in TAL)
- Absence of ADH –> distal tubule and cortical collecting duct impermeable to H2O
- Tubular fluid is diluted even more as solute is removed from tubular fluid in distal tubule and cortical collecting duct but water remains
- B/C of low fluid osmolality in collecting duct and slight permeability of medullary collecting duct to urea, urea enters the tubule from the medullary interstitium thereby keeping the osmolality of the medial interstitium low
What class of diuretics directly affects principal cells?
K+ sparing diuretics
reabsorbs 67% of the fluid and electrolytes filtered by the glomerulus
proximal tubule
segment responsible for concentrating urine
collecting duct
glaucoma
mannitol
acetazolamide
site of secretion of organic anions and cations
proximal tubule
always impermeable to water
thick ascending limb
permeable to water only in the presence of ADH
late distal tubule and collecting ducts
site of the Na+/2Cl-/K+ co transporter
thick ascending limb
site of isotonic fluid reabsorption
proximal tubule
site responsible for diluting urine
thick ascending limb
only site where glucose and amino acids are reabsorbed
proximal tubule
water reabsorption in the loop of henle
thin descending limb
Triamterene
K+ sparing
Acetazolamide
carbonic anhydrase inhibitor
Hydrochlorothiazide
thiazide diuretic
Bumetanide
loop
Spironolactone
K+ sparing diuretic (aldosterone antagonist)
Chlorothiazide
thiazide
Ethacrynic acid
loop (not a sulfa drug)
Mannitol
osmotic diuretic
Metolazone
thiazide diuretic
Chlorthalidone
thiazide diuretic
Furosemide
loop diuretic
Amiloride
K+ sparing diuretic
Torsemide
loop diuretic
acute pulmonary edema
loops
idiopathic hypercalciuria (–>calcium stones)
thiazide diuretics
mild to moderate CHF with expanded ECV
loops (maybe thiazide if mild)
in conjunction with loops or thiazides to retain K+
K+ sparing diuretics
edema associated with nephrotic syndrome
loop diuretic
increased intracranial pressure
mannitol
mild to moderate HTN
thiazides
hypercalcemia
loops
altitude sickness
acetazolamide
hyperaldosteronism
Spironolactone
What is the site of action of mannitol?
proximal convoluted tubule
What is the site of action of the thiazides?
distal convoluted tubule
A pt with heart failure exacerbation needs medical diuresis but has a sulfa allergy. What diuretic can be used?
Ethacrynic acid
