Distal tubule

Distal tubule

The distal tubule is involved in reabsorption of water, Na+ and Ca2+ ions. H+, NH4+, creatinine and drugs are actively secreted by this part of the renal tubule. Na+ions are resorbed via co-transport together with Cl- ions and via active transport of the Na+/K+-ATPase pump.

Aldosterone controls the exchange of Na+/K+ions. Water is reabsorbed via osmosis; this process is regulated by the pituitary hormone ADH. Ca2+ ions are resorbed by carrier-mediated transport, which is controlled by the parathyroid hormone (PTH). H+ ions are secreted via a process of countertransport with Na+ ions.


Which of the following factors does NOT increase potassium excretion? 


I Thiazide diuretics’ site of action is the distal tubule

II Thiazide diuretics are weaker than loop diuretics