<prompt> Number of aquaporins cloned is:5813None of the above  <response>: 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: Ganongs Review of Medical Physiology 23rd edition, Chapter 38. 