Nephron transport mechanisms, tubuloglomerular feedback, and acid-base compensation concepts tested on USMLE Step 1.
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- Where in the nephron does SGLT2-mediated Na+/glucose cotransport primarily occur?
- Early proximal convoluted tubule
- Approximately what percentage of filtered Na+ is reabsorbed in the proximal tubule?
- About 65 to 70 percent
- What percentage of filtered bicarbonate is reabsorbed in the proximal convoluted tubule?
- About 80 to 90 percent
- Which enzyme allows the proximal tubule brush border to convert CO2 and H2O for bicarbonate reabsorption?
- Carbonic anhydrase
- Which transporter mediates Na+, K+, and Cl- reabsorption in the thick ascending limb?
- Na-K-2Cl cotransporter (NKCC2)
- Loop diuretics act on which nephron transporter?
- The Na-K-2Cl cotransporter (NKCC2) in the thick ascending limb
- Is the thick ascending limb permeable to water?
- No, it is impermeable to water
- Which transporter mediates Na+ and Cl- reabsorption in the distal convoluted tubule?
- Na-Cl cotransporter (NCC)
- Thiazide diuretics act on which nephron transporter?
- The Na-Cl cotransporter (NCC) in the distal convoluted tubule
- In the collecting duct, what is the main function of principal cells?
- Reabsorb Na+ and secrete K+
- In the collecting duct, what is the main function of intercalated cells?
- Regulate acid-base balance by secreting H+ or HCO3-
- Which hormone increases Na+ reabsorption and K+ secretion by principal cells?
- Aldosterone
- Which channel does aldosterone upregulate in principal cells to increase Na+ reabsorption?
- Epithelial sodium channel (ENaC)
- Which hormone increases water permeability of the collecting duct?
- ADH (vasopressin)
- Which water channel does ADH insert into the luminal membrane of collecting duct cells?
- Aquaporin-2 (AQP2)