title: Role of apical H-K exchange and basolateral K channel in the regulation of intracellular pH in rat distal colon crypt cells.
abstract: An apical membrane ouabain-sensitive H-K exchange and a barium-sensitive basolateral membrane potassium channel are present in colonic crypt cells and may play a role in both K absorption and intracellular pH (pHi) regulation. To examine the possible interrelationship between apical membrane H-K exchange and basolateral membrane K movement in rat distal colon in the regulation of pHi, experiments were designed to assess whether changes in extracellular potassium can alter pHi. pHi in isolated rat crypts was determined using microspectrofluorimetric measurements of the pH-sensitive dye BCECF-AM (2', 7'-bis(carboxyethyl-5(6)-carboxy-fluorescein acetoxy methylester). After loading with the dye, crypts were superfused with a Na-free solution which resulted in a rapid and reversible fall in pHi (7.36 +/- 0.02 to 6.98 +/- 0.03). Following an increase in extracellular [K] to 20 mm, in the continued absence of Na, there was a further decrease in pHi (0.20 +/- 0.02, P < 0.01). K-induced acidification was blocked both by 2 mm bath barium, a K channel blocker, and by 0. 5 mm lumen ouabain. K-induced acidification was also observed when intracellular acidification was induced by a NH4Cl prepulse. These observations suggest that increased basolateral K movement increases intracellular [K] resulting in a decrease in pHi that is mediated by a ouabain-sensitive apical membrane H,K-ATPase. Our results demonstrate an interrelationship between basolateral K movement and apical H-K exchange in the regulation of pHi and apical K entry in rat distal colon.
authors.affiliation: Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: M
authors.initials: M
authors.lastname: Ikuma
authors.forename: H J
authors.initials: HJ
authors.lastname: Binder
authors.forename: J
authors.initials: J
authors.lastname: Geibel
mesh_terms: D000818:Animals; D017920:Antiporters / Q000187:drug effects / Q000378:metabolism*; D001464:Barium / Q000494:pharmacology; D016764:Cell Polarity; D003106:Colon / Q000166:cytology* / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D017506:H(+)-K(+)-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism*; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000166:cytology* / Q000378:metabolism; D007424:Intracellular Fluid / Q000378:metabolism; D017136:Ion Transport; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D027961:Potassium-Hydrogen Antiporters; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism
chemical_list: D017920:Antiporters; D015221:Potassium Channels; D027961:Potassium-Hydrogen Antiporters; D001464:Barium; D010042:Ouabain; D017506:H(+)-K(+)-Exchanging ATPase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium