Biomaterial Database

pH-dependent fluoride transport in intestinal brush border membrane vesicles. 1998

H He, and V Ganapathy, and C M Isales, and G M Whitford

Department of Oral Biology-Physiology, Medical College of Georgia, Augusta, GA 30912-1129, USA.

Fluoride (F) absorption from the rat stomach and urinary bladder, hamster cheek pouch, and the renal tubules of several species are pH gradient-dependent. These observations led to the hypothesis that F crosses these epithelia in the form of the undissociated acid, HF. Several recent reports, however, have provided evidence that F absorption from the rat small intestine is insensitive to the lumenal pH. We report here our evidence that F uptake by rabbit intestinal brush border membrane vesicles (BBMV) occurred rapidly and with an overshoot only in the presence of an inward-directed proton gradient. In the absence of a proton gradient or in the presence of an outward-directed gradient, F uptake was slow and without an overshoot. In the presence of an inward-directed proton gradient, F uptake was partially inhibited by DIDS and DEP but not by diBAC. PCMBS inhibited F uptake by up to 83% in a dose-response manner. DiBAC appeared to reduce intravesicular pH slightly but the other reagents had no effect. When the uptake buffer contained chloride or nitrate, F uptake was partially inhibited compared to the mannitol or gluconate controls. It was concluded that F transport across the rabbit intestinal BBMV occurs via a carrier-mediated process which may involve cotransport of F with H+ or exchange of F with OH-. The inhibitory effects of DIDS, DEP and PCMBS may occur by affecting this carrier-mediated transport.

UI	MeSH Term	Description	Entries
D007408	Intestinal Absorption	Uptake of substances through the lining of the INTESTINES.	Absorption, Intestinal
D007421	Intestine, Small	The portion of the GASTROINTESTINAL TRACT between the PYLORUS of the STOMACH and the ILEOCECAL VALVE of the LARGE INTESTINE. It is divisible into three portions: the DUODENUM, the JEJUNUM, and the ILEUM.	Small Intestine,Intestines, Small,Small Intestines
D007555	Isoxazoles	Azoles with an OXYGEN and a NITROGEN next to each other at the 1,2 positions, in contrast to OXAZOLES that have nitrogens at the 1,3 positions.	Isoxazole
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008353	Mannitol	A diuretic and renal diagnostic aid related to sorbitol. It has little significant energy value as it is largely eliminated from the body before any metabolism can take place. It can be used to treat oliguria associated with kidney failure or other manifestations of inadequate renal function and has been used for determination of glomerular filtration rate. Mannitol is also commonly used as a research tool in cell biological studies, usually to control osmolarity.	(L)-Mannitol,Osmitrol,Osmofundin
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
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
D009566	Nitrates	Inorganic or organic salts and esters of nitric acid. These compounds contain the NO3- radical.	Nitrate
D009994	Osmolar Concentration	The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.	Ionic Strength,Osmolality,Osmolarity,Concentration, Osmolar,Concentrations, Osmolar,Ionic Strengths,Osmolalities,Osmolar Concentrations,Osmolarities,Strength, Ionic,Strengths, Ionic
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.