Biomaterial Database

Transport of propionate by human ileal brush-border membrane vesicles. 1991

J M Harig, and K H Soergel, and J A Barry, and K Ramaswamy

Gastroenterology Division, Medical College of Wisconsin, Milwaukee 53226.

Human ileal brush-border membrane vesicles were employed to study the mechanisms of short-chain fatty acid (propionate) absorption especially to determine the effects of intravesicular HCO3- and the component of nonionic diffusion. Preloading the vesicles with HCO3- resulted in up to 20-fold "overshoots" of transport, and this effect was not seen with other intravesicular anions. This transport process was very fast (peak uptake 6 s) and was not due to intravesicular buffering by HCO3-. Radiolabeled propionate transport demonstrated transstimulation when the vesicles were preloaded with unlabeled propionate. An inward H+ gradient led to stimulation of propionate transport much smaller than in the presence of trans-HCO3-, whereas an inward Na+ gradient had no effect. Propionate transport was attenuated by the anion exchange inhibitors SITS and DIDS. Under HCO3- gradient conditions, propionate transport exhibited saturation kinetics with an apparent Km of 21 +/- 3 mM and a Vmax of 50 +/- 3 nmol.mg protein-1.3 s-1. Propionate transport was inhibited up to 40% by 2-5 carbon short-chain fatty acids (10 mM) but not by other organic anions. Short-chain fatty acid transport in the human ileum is Na+ independent and occurs mostly via a specific anion exchange mechanism with HCO3-. Our results also demonstrate a small component of nonionic diffusion of the protonated fatty acid (or anion exchange for OH-).

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.
D007413	Intestinal Mucosa	Lining of the INTESTINES, consisting of an inner EPITHELIUM, a middle LAMINA PROPRIA, and an outer MUSCULARIS MUCOSAE. In the SMALL INTESTINE, the mucosa is characterized by a series of folds and abundance of absorptive cells (ENTEROCYTES) with MICROVILLI.	Intestinal Epithelium,Intestinal Glands,Epithelium, Intestinal,Gland, Intestinal,Glands, Intestinal,Intestinal Gland,Mucosa, Intestinal
D007477	Ions	An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.
D007700	Kinetics	The rate dynamics in chemical or physical systems.
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
D011339	Probenecid	The prototypical uricosuric agent. It inhibits the renal excretion of organic anions and reduces tubular reabsorption of urate. Probenecid has also been used to treat patients with renal impairment, and, because it reduces the renal tubular excretion of other drugs, has been used as an adjunct to antibacterial therapy.	Benecid,Benemid,Benuryl,Pro-Cid,Probecid,Probenecid Weimer
D011422	Propionates	Derivatives of propionic acid. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxyethane structure.	Propanoate,Propanoic Acid,Propionate,Propanoates,Propanoic Acid Derivatives,Propanoic Acids,Propionic Acid Derivatives,Propionic Acids,Acid, Propanoic,Acids, Propanoic,Acids, Propionic,Derivatives, Propanoic Acid,Derivatives, Propionic Acid
D002264	Carboxylic Acids	Organic compounds containing the carboxy group (-COOH). This group of compounds includes amino acids and fatty acids. Carboxylic acids can be saturated, unsaturated, or aromatic.	Carboxylic Acid,Acid, Carboxylic,Acids, Carboxylic
D002712	Chlorides	Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.	Chloride,Chloride Ion Level,Ion Level, Chloride,Level, Chloride Ion