Biomaterial Database

Na+/H+ exchange by brush border membrane vesicles of human ileal small intestine. 1988

K Kikuchi, and N N Abumrad, and F K Ghishan

Department of Pediatrics, Vanderbilt University, Nashville, Tennessee.

Na+/H+ exchange was characterized in the ileum of human brush border membrane vesicles. We have used a well-validated technique for preparing ileal brush border membranes from human cadaveric small intestine. Sodium was transported into the intravesicular space as evident by an osmolality study, which showed negligible binding to the external surface of the vesicles. The presence of an outwardly directed pH gradient stimulated Na+ uptake compared with the no pH gradient condition. Maximal uptake occurred after 5 min with a threefold overshoot over equilibrium. The rate of Na+ uptake was dependent on the extent of the pH gradient generated across the vesicles. Amiloride at 10(-4) M concentration inhibited the initial rate of Na+ uptake by greater than 90% and prevented stimulation of Na+ uptake in the presence of an outwardly directed pH gradient. The imposition of negative membrane potential did not enhance Na+ uptake compared with voltage clamp condition under both pH gradient and no pH gradient conditions, indicating an electroneutral process. Kinetic analysis of the Na+/H+ exchanger at 5 s showed a maximum velocity of 23.2 +/- 0.3 nmol/mg protein.5 s and a Michaelis constant of 14.5 +/- 5.2 mM. These studies demonstrate the presence of a Na+/H+ exchanger in human ileal brush border membrane vesicles.

UI	MeSH Term	Description	Entries
D007082	Ileum	The distal and narrowest portion of the SMALL INTESTINE, between the JEJUNUM and the ILEOCECAL VALVE of the LARGE INTESTINE.
D007473	Ion Channels	Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.	Membrane Channels,Ion Channel,Ionic Channel,Ionic Channels,Membrane Channel,Channel, Ion,Channel, Ionic,Channel, Membrane,Channels, Ion,Channels, Ionic,Channels, Membrane
D008297	Male		Males
D008871	Microvilli	Minute projections of cell membranes which greatly increase the surface area of the cell.	Brush Border,Striated Border,Border, Brush,Border, Striated,Borders, Brush,Borders, Striated,Brush Borders,Microvillus,Striated Borders
D008875	Middle Aged	An adult aged 45 - 64 years.	Middle Age
D009940	Organoids	An organization of cells into an organ-like structure. Organoids can be generated in culture, e.g., self-organized three-dimensional tissue structures derived from STEM CELLS (see MICROPHYSIOLOGICAL SYSTEMS). They are also found in certain NEOPLASMS.	Organoid
D002102	Cadaver	A dead body, usually a human body.	Corpse,Cadavers,Corpses
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23