Choline transport in rat liver basolateral plasma membrane vesicles. 1996

R H Moseley, and H Takeda, and L J Zugger
Department of Internal Medicine, Veterans Affairs Medical Center, Ann Arbor, MI 48105, USA.

Previous studies have demonstrated several pathways for the sinusoidal uptake of endogenous and exogenous organic cations, including two distinct organic cation:H+ exchanges and a separate carrier-mediated system driven by the inside-negative membrane potential. In this study, the driving force(s) for the uptake of the endogenous quaternary amine, choline, were determined in rat liver basolateral plasma membrane (blLPM) vesicles. Choline uptake into an osmotically sensitive space was not stimulated by an outwardly directed H+ or inwardly directed Na+ gradient. Instead, an inside-negative K+ diffusion potential stimulated choline uptake, suggesting the presence of a conductive pathway for choline uptake in bILPM vesicles. Conductive choline uptake was confirmed by inducing variable changes in the transmembrane potential with anions of different membrane permeability. Choline uptake in blLPM vesicles exhibitied 1) temperature dependency; 2) trans-stimulation; and 3) saturability, with an approximate Michaelis constant (Km) of 0.34 mmol/L and maximum velocity (Vmax) of 0.45 nmol/mg protein/15 s. Choline uptake in blLPM vesicles was cis-inhibited by the structurally similar derivative, hemicholinium-3 and acetylcholine, but not by substrates for other organic cation transport processes identified in blLPM vesicles, including thiamine, tetraethylammonium (TEA), tri-n-butyl-methylammonium (TBuMA), and N'-methylnicotinamide (NMN). These findings demonstrate an electrogenic pathway on the sinusoidal membrane for the uptake of this essential nutrient and support the existence of multiple pathways for the sinusoidal uptake of endogenous and exogenous organic cations.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008099 Liver A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances. Livers
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.
D002462 Cell Membrane The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells. Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D002794 Choline A basic constituent of lecithin that is found in many plants and animal organs. It is important as a precursor of acetylcholine, as a methyl donor in various metabolic processes, and in lipid metabolism. Bursine,Fagine,Vidine,2-Hydroxy-N,N,N-trimethylethanaminium,Choline Bitartrate,Choline Chloride,Choline Citrate,Choline Hydroxide,Choline O-Sulfate,Bitartrate, Choline,Chloride, Choline,Choline O Sulfate,Citrate, Choline,Hydroxide, Choline,O-Sulfate, Choline
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
D000838 Anions Negatively charged atoms, radicals or groups of atoms which travel to the anode or positive pole during electrolysis. Anion
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

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