Pharmaceutical Research

, Volume 24, Issue 3, pp 575–584

Transport of Nicotinate and Structurally Related Compounds by Human SMCT1 (SLC5A8) and Its Relevance to Drug Transport in the Mammalian Intestinal Tract

  • Elangovan Gopal
  • Seiji Miyauchi
  • Pamela M. Martin
  • Sudha Ananth
  • Penny Roon
  • Sylvia B. Smith
  • Vadivel Ganapathy
Research Paper

Abstract

Purpose

To examine the involvement of human SMCT1, a Na+-coupled transporter for short-chain fatty acids, in the transport of nicotinate/structural analogs and monocarboxylate drugs, and to analyze its expression in mouse intestinal tract.

Materials and Methods

We expressed human SMCT1 in X. laevis oocytes and monitored its function by [14C]nicotinate uptake and substrate-induced inward currents. SMCT1 expression in mouse intestinal tract was examined by immunofluorescence.

Results

[14C]Nicotinate uptake was several-fold higher in SMCT1-expressing oocytes than in water-injected oocytes. The uptake was inhibited by short-chain/medium-chain fatty acids and various structural analogs of nicotinate. Exposure of SMCT1-expressing oocytes to nicotinate induced Na+-dependent inward currents. Measurements of nicotinate flux and associated charge transfer into oocytes suggest a Na+:nicotinate stoichiometry of 2:1. Monocarboxylate drugs benzoate, salicylate, and 5-aminosalicylate are also transported by human SMCT1. The transporter is expressed in the small intestine as well as colon, and the expression is restricted to the lumen-facing apical membrane of intestinal and colonic epithelial cells.

Conclusions

Human SMCT1 transports not only nicotinate and its structural analogs but also various monocarboxylate drugs. The transporter is expressed on the luminal membrane of the epithelial cells lining the intestinal tract. SMCT1 may participate in the intestinal absorption of monocarboxylate drugs.

Key words

SMCT1 intestinal tract monocarboxylate drugs aminosalicylates electrophysiology 

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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Elangovan Gopal
    • 1
  • Seiji Miyauchi
    • 1
  • Pamela M. Martin
    • 1
  • Sudha Ananth
    • 1
  • Penny Roon
    • 2
  • Sylvia B. Smith
    • 2
  • Vadivel Ganapathy
    • 1
  1. 1.Departments of Biochemistry and Molecular BiologyMedical College of GeorgiaAugustaUSA
  2. 2.Departments of Cellular Biology and AnatomyMedical College of GeorgiaAugustaUSA

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