title: Differential localization of colonic H(+)-K(+)-ATPase isoforms in surface and crypt cells.
abstract: Two distinct colonic H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase) isoforms can be identified in part on the basis of their sensitivity to ouabain. The colonic H(+)-K(+)-ATPase alpha-subunit (HKc alpha) was recently cloned, and its message and protein are present in surface (and the upper 20% of crypt) cells in the rat distal colon. These studies were performed to establish the spatial distribution of the ouabain-sensitive and ouabain-insensitive components of both H(+)-K(+)-ATPase activity in apical membranes prepared from surface and crypt cells and K(+)-dependent intracellular pH (pHi) recovery from an acid load both in isolated perfused colonic crypts and in surface epithelial cells. Whereas H(+)-K(+)-ATPase activity in apical membranes from surface cells was 46% ouabain sensitive, its activity in crypt apical membranes was 96% ouabain sensitive. Similarly, K(+)-dependent pHi recovery in isolated crypts was completely ouabain sensitive, whereas in surface cells K(+)-dependent pHi recovery was insensitive to ouabain. These studies provide compelling evidence that HKc alpha encodes the colonic ouabain-insensitive H(+)-K(+)-ATPase and that a colonic ouabain-sensitive H(+)-K(+)-ATPase isoform is present in colonic crypts and remains to be cloned and identified.
authors.affiliation: Department of Internal Medicine, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: V M
authors.initials: VM
authors.lastname: Rajendran
authors.forename: S K
authors.initials: SK
authors.lastname: Singh
authors.forename: J
authors.initials: J
authors.lastname: Geibel
authors.forename: H J
authors.initials: HJ
authors.lastname: Binder
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D003106:Colon / Q000166:cytology / Q000201:enzymology*; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013499:Surface Properties
chemical_list: D007527:Isoenzymes; D001464:Barium; D010042:Ouabain; D017506:H(+)-K(+)-Exchanging ATPase; D011188:Potassium