title: K(+)-H+ exchange activity in brush-border membrane vesicles isolated from chick small intestine.
abstract: The purpose of this study was to investigate the presence of a K(+)-H+ exchanger in brush-border membrane vesicles (BBMV) isolated from chick small intestine. 86Rb+, as a tracer for K+ transport, was used to probe for the exchange mechanism. An outwardly directed proton gradient (pH 5.5 inside, pH 7.5 outside) stimulated 86Rb+ uptake into voltage-clamped BBMV. H(+)-driven 86Rb+ uptake was only weakly inhibited by 5-(N-ethyl-N-isopropyl)amiloride, whereas this agent strongly inhibited H(+)-driven Na+ uptake. At initial rates, proton-driven 86Rb+ uptake was significantly reduced by external K+ but it was not significantly affected by external Na+. Conversely, extravesicular Na+ inhibited proton-driven Na+ uptake, whilst K+ had little effect. H(+)-driven K+ uptake tended to saturate with increasing external K+ concentrations and Lineweaver-Burk analysis of the data revealed a Km for external K+ of 2 mM. These findings are consistent with the presence of K(+)-H+ exchange activity in the chicken jejunal brush-border membrane.
authors.affiliation: Departamento de Fisiología y Biología Animal, Facultad de Farmacia, Universidad de Sevilla, Spain.
authors.forename: M J
authors.initials: MJ
authors.lastname: Peral
authors.forename: M
authors.initials: M
authors.lastname: Cano
authors.forename: A A
authors.initials: AA
authors.lastname: Ilundáin
mesh_terms: D000818:Animals; D017920:Antiporters / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002645:Chickens; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000494:pharmacology; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D017136:Ion Transport; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D027961:Potassium-Hydrogen Antiporters; D011485:Protein Binding; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
chemical_list: D017920:Antiporters; D007093:Imidazoles; D027961:Potassium-Hydrogen Antiporters; C035235:Sch 28080; D006859:Hydrogen; D012964:Sodium; D012413:Rubidium; D011188:Potassium