Document Detail

Carrier-mediated uptake of nicotinic acid by rat intestinal brush-border membrane vesicles and relation to monocarboxylic acid transport.
MedLine Citation:
PMID:  2273446     Owner:  NLM     Status:  MEDLINE    
The intestinal transport of [14C]nicotinic acid was investigated at 27 degrees C by using brush-border membrane vesicles (BBMV) isolated from the rat small intestine. The osmolarity sensitive uptake by BBMV showed a remarkable overshoot phenomenon in the presence of an inward-directed H+ gradient (pHin = 7.5, pHout = 6.0). In contrast, the imposition of a Na+ gradient ([Na+]in = 0 mM, [Na+]out = 100 mM) had no stimulatory effect on the uptake of [14C]nicotinic acid. The remarkable pH-dependence of the initial uptake showing an increase of the uptake rate with decreasing the extravesicular pH disappeared completely in the presence of a structural analogue, isonicotinic acid, at pH below 6.5. In the presence of a H+ gradient, the initial uptake of [14C]nicotinic acid was saturable with the apparent Kt of 4.43 mM and Jmax of 2.55 nmol/mg protein/15 s. The uptake was increased by the imposition of an inside-positive membrane potential and was significantly inhibited by monocarboxylic acids such as benzoic acid, salicylic acid, acetic acid, propionic acid, valproic acid and L-lactic acids as well as two isomers (isonicotinic acid and picolinic acid). The uptake was not inhibited by nicotinamide, nicotinyl alcohol, D-glucose, p-aminohippuric acid, glycyl-L-proline, succinic acid and an exchange transport inhibitor. From these results it was concluded that nicotinic acid is transported through the intestinal brush-border membrane by a carrier-mediated system and the system can recognize some acidic drugs with a monocarboxylic group. The pH dependent intestinal uptake of nicotinic acid can be ascribed to the proton-coupled and active carrier-mediated transport mechanism rather than a simple diffusion of the undissociated nicotinic acid to follow a pH-partition hypothesis.
M T Simanjuntak; I Tamai; T Terasaki; A Tsuji
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of pharmacobio-dynamics     Volume:  13     ISSN:  0386-846X     ISO Abbreviation:  J. Pharmacobio-dyn.     Publication Date:  1990 May 
Date Detail:
Created Date:  1991-02-25     Completed Date:  1991-02-25     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7901854     Medline TA:  J Pharmacobiodyn     Country:  JAPAN    
Other Details:
Languages:  eng     Pagination:  301-9     Citation Subset:  IM    
Faculty of Pharmaceutical Sciences, Kanazawa University, Japan.
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MeSH Terms
Biological Transport
Carboxylic Acids / pharmacokinetics*,  pharmacology
Extracellular Space / metabolism
Hydrogen-Ion Concentration
Intestinal Absorption
Intestine, Small / metabolism,  ultrastructure
Membrane Potentials / physiology
Membranes / metabolism
Microvilli / metabolism*,  ultrastructure
Niacin / pharmacokinetics*
Osmolar Concentration
Rats, Inbred Strains
Sodium / pharmacology
Reg. No./Substance:
0/Carboxylic Acids; 59-67-6/Niacin; 7440-23-5/Sodium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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