Abstract | BACKGROUND AND PURPOSE: EXPERIMENTAL APPROACH: In vitro investigations of ALA affinity for and uptake via SLC36A1 and SLC15A1 were performed in Caco-2 cell monolayers. Interaction of ALA with SLC15A1 was investigated in MDCK/SLC15A1 cells, whereas interactions with SLC36A1 were investigated in COS-7 cells transiently expressing SLC36A1. KEY RESULTS: ALA inhibited SLC36A1-mediated L-[(3)H]Pro and SLC15A1-mediated [(14)C] Gly-Sar uptake in Caco-2 cell monolayers with IC(50) values of 11.3 and 2.1 mM respectively. In SLC36A1-expressing COS-7 cells, the uptake of [(14)C]ALA was saturable with a K(m) value of 6.8 +/- 3.0 mM and a V(max) of 96 +/- 13 pmol x cm(-2) x min(-1). Uptake of [(14)C]ALA was pH and concentration dependent, and could be inhibited by glycine, proline and GABA. In a membrane potential assay, translocation of ALA via SLC36A1 was concentration dependent, with a K(m) value of 3.8 +/- 1.0 mM. ALA is thus a substrate for SLC36A1. In Caco-2 cells, apical [(14)C]ALA uptake was pH dependent, but Na(+) independent, and completely inhibited by 5-hydroxy-L-tryptophan and L-4,4'-biphenylalanyl-l-proline. CONCLUSIONS AND IMPLICATIONS. ALA was a substrate for SLC36A1, and the apical absorption in Caco-2 cell was only mediated by SLC36A1 and SLC15A1. This advances our understanding of intestinal absorption mechanisms of ALA, as well as its potential for drug interactions.
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Authors | S Frølund, O C Marquez, M Larsen, B Brodin, C U Nielsen |
Journal | British journal of pharmacology
(Br J Pharmacol)
Vol. 159
Issue 6
Pg. 1339-53
(Mar 2010)
ISSN: 1476-5381 [Electronic] England |
PMID | 20128809
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Amino Acid Transport Systems
- Oligopeptides
- Peptide Transporter 1
- Photosensitizing Agents
- SLC15A1 protein, human
- SLC36A1 protein, human
- Symporters
- Aminolevulinic Acid
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Topics |
- Amino Acid Transport Systems
(metabolism)
- Aminolevulinic Acid
(pharmacokinetics, pharmacology)
- Animals
- Biological Transport
- COS Cells
- Caco-2 Cells
- Chlorocebus aethiops
- Dose-Response Relationship, Drug
- Humans
- Intestinal Absorption
- Intestinal Mucosa
(metabolism)
- Membrane Potentials
(drug effects)
- Oligopeptides
(pharmacokinetics, pharmacology)
- Peptide Transporter 1
- Photosensitizing Agents
(pharmacokinetics, pharmacology)
- Substrate Specificity
- Symporters
(metabolism)
- Transfection
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