Diuretics Flashcards
What are the different classes of diuretics?
Thiazide diuretics Loop diuretics Potassium-sparing diuretics Carbonic anhydrase inhibitors Osmotic diuretics
How much of the blood plasma that enters the kidneys is filtered into the Bowman capsule?
16-20%
What substances are reabsorbed in the proximal convoluted tubule?
Nearly all glucose, bicarbonate, water, and amino acids. 2/3 of sodium is reabsorbed as well.
What substance modulates the reabsorption of bicarbonate?
Carbonic anhydrase
What type of drug (and specifically, what is the name of this drug) would inhibit bicarbonate reabsorption?
Carbonic anhydrase inhibitor; acetazolamide.
Which substances, if found in tubular fluid, would prevent water reabsorption?
Mannitol and glucose; this would result in osmotic diuresis.
Which part of the nephron contains the acid and base secretory systems?
Proximal convoluted tubule
What are a few organic acids that may be secreted through the acid secretory system?
Uric acid, antibiotics, diuretics
Why does hyperuricemia occur with certain diuretic drugs?
Most diuretics enter the nephron at the acid secretory system, competing with uric acids for secretion. This increases the levels of uric acid left in the blood.
Which specific substances are secreted by the base secretory system?
Creatine and choline
True or false: Although the filtrate that leaves the proximal convoluted tubule is isotonic, by the time it has passed through the descending loop of Henle, the salt concentration has increased 3x.
True, through countercurrent mechanisms.
True or false: The ascending loop of Henle is permeable to water.
False; it is impermeable to water (as is the distal convoluted tubule.
Sodium, potassium, chloride are actively reabsorbed in the ascending loop of Henle. What is the mechanism of reabsorption?
A Na+/K+/2Cl- cotransporter.
How much of the tubular sodium chloride is reabsorbed in the ascending loop of Henle, and what connotation does this have in choosing a diuretic drug?
25-30%; this makes the ascending loop of Henle a good target for diuretic drugs (loop diuretics, which are the most efficacious diuretics)
Which class of diuretics affects the distal convoluted tubule, and what is its specific target?
Thiazides; they target the Na+/Cl- transporter (responsible for reabsorption of about 10% of the filtered NaCl)
What factors influence calcium reabsorption or secretion?
Calcium is reabsorbed through a Na+/Ca2+ exchanger; its secretion is regulated by parathyroid hormone.
In the collecting tubule and duct, what substances inhibit the epithelial sodium channels, preventing sodium reabsorption?
Amiloride and triamterene.
What is the effect of aldosterone in the collecting tubule and duct?
It increases sodium reabsorption
What is the effect of ADH in the collecting tubule and duct?
It increases water reabsorption
What is the underlying cause of an edematous state?
Abnormally high amounts of sodium are reabsorbed, leading to high retention of water.
How does the kidney respond to the reduced CO of heart failure, and what class of diuretics are commonly used in this case?
As if there were a decrease in blood volume: more salt is reabsorbed, leading to water retention so as to increase blood volume. Loop diuretics are commonly used in this situation.
What is hepatic ascites?
Accumulation of fluid in the abdominal cavity as a complication of cirrhosis of the liver.
How does secondary hyperaldosteronism complicate hepatic ascites, and which drug is useful for this effect?
Fluid retention is promoted by aldosterone; aldosterone levels were increased in response to decreased blood volume. This increases the fluid accumulation. Spironolactone (potassium-sparing) is useful in this situation.