Observations on folate absorption with particular reference to folate polyglutamate and possible inhibitors to its absorption

Perry, Janet; Chanarin, I.

doi:10.1136/gut.13.7.544

Cited by 35 publications

(13 citation statements)

References 23 publications

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“…It has been reported that sulfobromophthalein and 4,4Ј-diisothiocyanostilbene-2,2Ј-disulfonic acid are inhibitors of pH-sensitive folate transport in the small intestine (Perry and Chanarin, 1972;Schron et al, 1985). Consistent with that, we found that both of them inhibit folate transport mediated by hPCFT/HCP1 significantly (Fig.…”

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confidence: 80%

Functional Characterization of Human Proton-Coupled Folate Transporter/Heme Carrier Protein 1 Heterologously Expressed in Mammalian Cells as a Folate Transporter

Nakai¹,

Inoue²,

Abe³

et al. 2007

J Pharmacol Exp Ther

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The functional characteristics of human proton coupled folate transporter (hPCFT)/heme carrier protein (HCP) 1 were investigated. hPCFT/HCP1 expressed transiently in human embryonic kidney 293 cells mediated the transport of folate at an acidic extracellular pH of 5.5 in a manner independent of Na ϩ and insensitive to membrane potential, but its transport activity was absent at near-neutral pH. Folate transport mediated by hPCFT/hHCP1 at pH 5.5 was saturable with a K m of 1.67 M and extensively inhibited by reduced folates, such as folinate, 5-methyltetrahydrofolate, and methotrexate (MTX). Sulfobromophthalein and 4,4Ј-diisothiocyanostilbene-2,2Ј-disulfonic acid were also found to be potent inhibitors of hPCFT/hHCP1, but hemin was found to exhibit only minimal inhibitory effect.When expressed stably as a protein fused with green fluorescent protein (GFP-hPCFT/HCP1) in MDCKII cells, GFP-hPCFT/ HCP1 was mainly localized at the apical membrane, and the cellular accumulation of MTX was higher from the apical side than from the basal side. These functional features of hPCFT/ HCP1 are consistent with those of the well characterized carrier-mediated folate transport system in the small intestine, suggesting that hPCFT/HCP1 is responsible for the intestinal absorption of folate and also MTX. We also found that sulfasalazine is a potent inhibitor of hPCFT/HCP1, which would interfere with the intestinal absorption of MTX when coadministered in therapy for rheumatoid arthritis as well as folate.

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confidence: 80%

Functional Characterization of Human Proton-Coupled Folate Transporter/Heme Carrier Protein 1 Heterologously Expressed in Mammalian Cells as a Folate Transporter

Nakai¹,

Inoue²,

Abe³

et al. 2007

J Pharmacol Exp Ther

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“…Malabsorption of folate has been reported to occur (4-6) but has not been confirmed (7)(8)(9)(10)(11).…”

Section: Introductionmentioning

confidence: 99%

Effect of anticonvulsant drugs on the rate of folate catabolism in mice.

Kelly¹,

Weir²,

Reed³

et al. 1979

J. Clin. Invest.

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“…In persons with normal folate levels, phenytoin is unable to depress the intestinal ab sorption of folic acid [18]. Once established, folate deficiency may cause alterations in the intestinal mucosa morphology and function [3], and this gastrointestinal dysfunction may be corrected by parenteral folic acid alone [8].…”

Section: Discussionmentioning

confidence: 99%

Inhibition of Intestinal Absorption of Folic Acid by Phenytoin

Elsborg¹

1974

Acta Haematol

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Folate deficiency in four patients could be ascribed to anticonvulsant therapy with phenytoin. Their intestinal absorption of folic acid was depressed only when phenytoin was given simultaneously. Otherwise the absorption of folic acid was normal. This malabsorption of folic acid is probably due to a rise in the jejunal pH produced by phenytoin. It is assumed, however, that this effect of phenytoin is rather the result than the cause of folate deficiency occurring during anticonvulsant drug therapy.

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Observations on folate absorption with particular reference to folate polyglutamate and possible inhibitors to its absorption

Cited by 35 publications

References 23 publications

Functional Characterization of Human Proton-Coupled Folate Transporter/Heme Carrier Protein 1 Heterologously Expressed in Mammalian Cells as a Folate Transporter

Functional Characterization of Human Proton-Coupled Folate Transporter/Heme Carrier Protein 1 Heterologously Expressed in Mammalian Cells as a Folate Transporter

Effect of anticonvulsant drugs on the rate of folate catabolism in mice.

Inhibition of Intestinal Absorption of Folic Acid by Phenytoin

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