Medical Electron Microscopy

, Volume 37, Issue 2, pp 71–80 | Cite as

Aquaporins in the digestive system

  • Toshiyuki Matsuzaki
  • Yuki Tajika
  • Abdushukur Ablimit
  • Takeo Aoki
  • Haruo Hagiwara
  • Kuniaki Takata
REVIEW

Abstract

Fluid transfer such as secretion and absorption is one of the major functions of the digestive system. Aquaporins are water channel proteins providing water transfer across the cellular membrane. At least six aquaporin isoforms are expressed in the digestive system. Aquaporin-1 (AQP1) is widely distributed in endothelial cells of capillaries and small vessels as well as in the central lacteals in the small intestine. AQP1 is also present in the duct system in the pancreas, liver, and bile duct. AQP3 is mainly expressed in the epithelia of the upper digestive tract from the oral cavity to the stomach and of the lower digestive tract from the distal colon to the anus. AQP4 is present in the parietal cells of the stomach and in the intestinal epithelia. AQP5 is expressed in acinar cells of the salivary, pyloric, and duodenal glands. AQP8 is expressed in the intestinal epithelia, salivary glands, pancreas, and liver. AQP9 is present in the liver and intestinal goblet cells. Aquaporins have important roles in the digestive system, such as AQP5 in saliva secretion, as shown by the studies on AQP5-null mice. In addition, water transfer across the digestive epithelia seems to occur not only via aquaporins but also via other transporter or channel systems.

Key words

Aquaporin AQP Water channel Digestive system Water Localization 

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Copyright information

© Springer-Verlag Tokyo 2004

Authors and Affiliations

  • Toshiyuki Matsuzaki
    • 1
  • Yuki Tajika
    • 1
  • Abdushukur Ablimit
    • 1
  • Takeo Aoki
    • 1
  • Haruo Hagiwara
    • 1
  • Kuniaki Takata
    • 1
  1. 1.Department of Anatomy and Cell BiologyGunma University Graduate School of MedicineGunmaJapan

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