QuestionSBA
QuestionChoice
Correct - Loop diuretics increase the amount of NaCl delivered to the distal nephron through inhibition of the Na/2Cl/K transporter. NaCl remains in the tubule of the thick ascending loop of Henley, reducing the osmotic concentration of the renal medulla. This therefore causes more water to be excreted as urine.
10008250
a
Loop Diuretics
QuestionChoice
Incorrect - Thiazide diuretics inhibit the Na+/Cl- co-transporter within the early distal tubule. These drugs are weaker and produce only a moderate diuresis, but are typically well tolerated. They last longer than loop diuretics but exert a lesser effect on the concentration gradient of the medulla.
10008252
c
Thiazide Diuretics
QuestionChoice
Incorrect - Carbonic anhydrase inhibitors block the reabsorption of HCO3, Na, and prevent the exchange and secretion of H+. Preventing the reabsorption of Na induces diuresis and there is decreased H+ formation inside the cell. This reduces the activity of the Na/H antiporter, and increases Na and HCO3 concentration in the lumen.
10008254
e
Carbonic Anhydrase Inhibitors
QuestionChoice
Incorrect - Osmotic diuretics increase the osmolality of the filtrate and reduce water reabsorption. They act best where most osmotic reabsorption occurs (i.e. the proximal tubule and descending loop of Henle). They do not work on a transporter.
10008253
d
Osmotic Diuretics
QuestionChoice
Incorrect - Potassium-sparing diuretics act on principle cells in the late distal and cortical collecting tubule. They inhibit either sodium channels or mineralocorticoid receptors, reducing potassium secretion into the tubular lumen. They do not affect the osmotic gradient of the medulla, or the transporter associated with it.
10008251
b
Potassium-sparing Diuretics
Concept
Chapter
2693
4655
Effect of Loop Diuretics on Calcium Excretion
Topic
188
Renal Pharmacology
14197
A 76-year-old woman with a history of congestive heart failure and hypertension presents with dyspnoea and orthopnoea. She denies having chest pain, chills, or fever. On examination you note pitting oedema in her ankles. A diuretic is prescribed to relieve her symptoms.

Which of the following classes of diuretics inhibits the action of the transporter that is primarily involved in generating the osmotic gradient in the medulla?
a