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. Author manuscript; available in PMC: 2019 Apr 2.
Published in final edited form as: N Engl J Med. 2015 Apr 2;372(14):1349–1358. doi: 10.1056/NEJMra1404726

Figure 4. Collecting-Duct Principal Cell.

Figure 4.

In the presence of vasopressin, water enters the principal cell from the lumen through aquaporin-2 (right) and exitsto the interstitium through aquaporin-3 and aquaporin-4. Regulation of aquaporin-2 by vasopressin is a result ofcyclic AMP (cAMP)–dependent activation of a protein kinase network that causes increased transcription of AQP2and redistribution of aquaporin-2 to the luminal membrane. The redistribution results from inhibition of aquaporin-2 endocytosis and stimulation of aquaporin-2 exocytosis. Intercalated cells mediate acid–base transport andare thought to be water-impermeable. Gαs denotes heterotrimeric G-protein alpha subunit.