This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diuretic, Subject name: Pharmacology
The site of action of the loop diuretic furosemide is: 
Select and explain. 
A. Thick ascending limb of loop of Henle, B. Descending limb of loop of Henle, C. Proximal convoluted tubule, D. Distal convoluted tubule
A: Thick ascending limb of loop of Henle
Answer: A: Thick ascending limb of loop of Henle 
Explanation: Ans. a. Thick ascending limb of loop of Henle (Ref: Goodman and Gilman : 12/e p678)The site of action of the loop diuretic furosemide is thick ascending limb of loop of Henle.DiureticSite of actionMechanism of actionCarbonic anbydrase inhibitorsProximal tubuleInhibit Na+ and HCO3 - absorption due to carbonic anhydraseQOsmotic diureticsLoop of HenleReduce renal medullary tonicityLoop diureticsThick ascending limb of loop of HenleInhibit Na+ - K+ 2CI- symporterQThiazidesEarly distal tubuleInhibit Na+ - Cl- symporterQAmilorideLate distal tubule, Collecting ductInhibit epithelial sodium channels (ENaC)QTrimaterenceLate distal tubule, Collecting ductInhibit epithelial sodium channels (ENaC)QAldosterone receptor antagonistsLate distal tubule, Collecting ductAntagonize the Na+ and H2O reabsorption due to aldosterone