Proximal Tubule

Question 1

Carbonic anhydrase inhibitors

Answer 1

Acetazolamide

Question 2

Carbonic anhydrase inhibitors MOA

Answer 2

• -prevent normal breakdown of carbonic acid…diminishes HCO3 reabsorption
• -…NaH antiporter is also involved in NaCl reabsorption….so inhibits proximal tubule NaCl reabsorption
• -….osmotic gradient for water reabsorption is decreased…increased delivery of NaHCO3, NaCl, and H2O to remaining nephron
• -…Thick ascending limb of Henle can handle it so much of increased delivery of NaCl is reabsorbed in the thick ascending
• -…the rest of nephron can’t handle bulk reabsorption of NaHCO3, so moderate increase in sodium and bicarbonate in urine and increase in urinary flow

Question 3

C.A. inhibitors… results

Answer 3

bicarb loss in urine
(C.A….90% in PT and 10% in DCT)

alkaline urine (b/c of NaHCO3)
enhanced Cl reabsorption...hyperchlormic acidosis)

Question 4

C.A. inhibitors… clinical uses

Answer 4

• -limited use as diuretics
• -to alkaliinize urine (cysteinurea)
• -reduce intra ocular pressure
• -management of seizures (MOA unknown)
• -prophylactic for mountain sickness

Question 5

CA inhibitors…side effects

Answer 5

• -metabolic acidosis

- -markedly increased K loss in urine=acute effect (1 day)