Biomaterial Database

Uptake of riboflavin by intestinal basolateral membrane vesicles: a specialized carrier-mediated process. 1993

H M Said, and D Hollander, and R Mohammadkhani

Medical Research Service, VA Medical Center, Long Beach, CA 90822.

The mechanism of riboflavin (RF) uptake by intestinal basolateral membrane vesicles (BLMV) was examined in this study. BLMV were isolated by an established Percoll-gradient methodology from rabbit small intestine. Uptake of riboflavin was mainly the result of transport of the substrate into an osmotically active intravesicular space with less binding to membrane surfaces. Uptake of RF with time was similar in the presence of a Na+ and a K+ gradient (out > in) and was not significantly influenced by changes in incubation buffer pH. The initial rate of uptake of riboflavin as a function of concentration was saturable in both jejunal and ileal BLMV and occurred with apparent Km values of 5.0 microM and 4.4 microM and Vmax values of 91.6 and 60.8 pmol/mg protein per 5 s, respectively. Unlabeled riboflavin and the structural analogues lumiflavin, isoriboflavin and 8-aminoriboflavin all caused significant inhibition (but to different degrees) in the uptake of [3H]riboflavin. On the other hand, 8-hydroxyriboflavin, lumichrome, lumazine and D-ribose failed to inhibit [3H]riboflavin uptake. Trans-stimulation of [3H]riboflavin efflux from preloaded BLMV by unlabeled riboflavin or lumiflavin was also observed. Altering transmembrane electrical potential by anion substitution and valinomycin-induced K+ diffusion did not affect the riboflavin uptake process. These results demonstrate the existence of a specialized carrier-mediated mechanism for riboflavin uptake by intestinal BLMV. Furthermore, the system appears to transport the vitamin by a process which is Na(+)- and pH-independent, and electroneutral in nature.

UI	MeSH Term	Description	Entries
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
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
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
D011817	Rabbits	A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes.	Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
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
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001692	Biological Transport	The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.	Transport, Biological,Biologic Transport,Transport, Biologic
D012256	Riboflavin	Nutritional factor found in milk, eggs, malted barley, liver, kidney, heart, and leafy vegetables. The richest natural source is yeast. It occurs in the free form only in the retina of the eye, in whey, and in urine; its principal forms in tissues and cells are as FLAVIN MONONUCLEOTIDE and FLAVIN-ADENINE DINUCLEOTIDE.	Vitamin B 2,Vitamin G,Vitamin B2
D012856	4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid	A non-penetrating amino reagent (commonly called SITS) which acts as an inhibitor of anion transport in erythrocytes and other cells.	4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid, Disodium Salt,SITS,SITS Disodium Salt,4 Acetamido 4' isothiocyanatostilbene 2,2' disulfonic Acid,Disodium Salt, SITS
D017878	4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid	An inhibitor of anion conductance including band 3-mediated anion transport.	4,4'-Diisothiocyano-2,2'-Stilbene Disulfonic Acid,DIDS