Number of aquaporins cloned is:: (A) 5, (B) 8, (C) 13, (D) None of the above
Answer is C. Rapid diffusion of water across cell membranes depends on the presence of water channels, integral membrane proteins called aquaporins. To date, 13 aquaporins have been cloned; however, only 4 aquaporins (aquaporin-1, aquaporin-2, aquaporin-3, and aquaporin-4) play a key role in the kidney. The roles played by aquaporin-1 and aquaporin-2 in renal water transpo are discussed below. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 38.