title: Apical ouabain-sensitive K+-activated-ATPase activity in colon and caecum of the chick.
abstract: This study sought to investigate the presence and characteristics of K+-ATPase activity in chicken intestinal epithelia. A cytochemical method revealed Na+-independent, ouabain-sensitive, K+-ATPase activity in the apical, but not in the basolateral, membrane of chicken colonic and caecal epithelial cells. K+-ATPase activity was not observed in the small intestine. The measurement of K+-activated pNPPase activity was used to characterize the K+-ATPase activity evidenced by the cytochemical method. In addition, K+ and NH4+, but neither Na+ nor Li+, could activate pNPPase activity in chicken intestinal epithelia. Vanadate abolished ouabain-sensitive, K+-activated pNPPase activity in the three membrane preparations tested, whereas oligomycin and SCH 28080 were without effect. The Km for K+ and the ouabain IC50 values for the apical colonic and caecal K+-activated pNPPase activity were higher than those measured for K+-activated pNPPase activity measured in the basolateral membrane of chicken jejunal enterocytes. The results indicate that the apical membranes of chicken colon and caecum possess Na+-independent, ouabain-sensitive K+-activated-ATPase activity.
authors.affiliation: Departamento de Fisiología y Biología Animal, Facultad de Farmacia, Universidad de Sevilla, C) Tramontana s/n, E-41012 Seville, Spain.
authors.forename: M L
authors.initials: ML
authors.lastname: Calonge
authors.forename: C
authors.initials: C
authors.lastname: De la Horra
authors.forename: M
authors.initials: M
authors.lastname: Cano
authors.forename: I
authors.initials: I
authors.lastname: Sánchez-Aguayo
authors.forename: A A
authors.initials: AA
authors.lastname: Ilundáin
mesh_terms: D000251:Adenosine Triphosphatases / Q000187:drug effects*; D000818:Animals; D027682:Cation Transport Proteins; D002432:Cecum / Q000187:drug effects* / Q000648:ultrastructure; D002645:Chickens; D003106:Colon / Q000187:drug effects* / Q000648:ultrastructure; D004305:Dose-Response Relationship, Drug; D010042:Ouabain / Q000494:pharmacology*
chemical_list: D027682:Cation Transport Proteins; D010042:Ouabain; D000251:Adenosine Triphosphatases; C022761:potassium transporting ATPase