Lessons from genetically engineered animal models VIII. Absorption and secretion of ions in the gastrointestinal tract.
Absorption and secretion of ions in gastrointestinal and other epithelial tissues require the concerted activities of ion pumps, channels, symporters, and exchangers, which operate in coupled systems to mediate transepithelial transport. Our understanding of the identities, membrane locations, and biochemical activities of epithelial ion transporters has advanced significantly in recent years, but major gaps and uncertainties remain in our understanding of their physiological functions. Increasingly, this problem is being addressed by the analysis of mutant mouse models developed by gene targeting. In this review, we discuss gene knockout studies of the secretory isoform of the Na(+)-K(+)-2Cl(-) cotransporter, isoforms 1, 2, and 3 of the Na(+)/H(+) exchanger, and the colonic H(+)-K(+)-ATPase. This approach is leading to a clearer understanding of the functions of these transporters in the living animal.
Shull
G E
GE
Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, 45267, USA. shullge@ucmail.uc.edu
Miller
M L
ML
Schultheis
P J
PJ
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology; D004064:Digestive System / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005818:Genetic Engineering; D017506:H(+)-K(+)-Exchanging ATPase / Q000235:genetics / Q000502:physiology; D007477:Ions; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000502:physiology; D028021:Sodium-Potassium-Chloride Symporters
D002352:Carrier Proteins; D007477:Ions; D017923:Sodium-Hydrogen Exchangers; D028021:Sodium-Potassium-Chloride Symporters; D017506:H(+)-K(+)-Exchanging ATPase