ArticleThe Journal of membrane biology1988
Anion specificity of the jejunal folate carrier: effects of reduced folate analogues on folate uptake and efflux.
Article in The Journal of membrane biology, 1988. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 2 papers.
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
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Who cites it
2 citing papers in PubMed, 12 citations in OpenAlex.
- Transport of pteroylglutamic acid into brush border membrane vesicles from rat small intestine is a partially carrier-mediated process.Zeitschrift fur Ernahrungswissenschaft · 1991Article
- pH modulation of the kinetics of rabbit jejunal, brush-border folate transport.The Journal of membrane biology · 1991Article
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3 authors at 1 institution in 1 country.
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Abstract
We previously reported that 3H-folate uptake by rabbit jejunal brush-border membrane (BBM) vesicles was markedly stimulated by an outwardly directed OH- gradient (pHin 7.7, pHout 5.5), inhibited by anion exchange inhibitors (DIDS, SITS, furosemide), and saturable (folate Km = 0.19 microM) suggesting carrier-mediated folate/OH- exchange (or H+/folate cotransport). In the present study, the anion specificity of this transport process was examined. Under conditions of an outwardly directed OH- gradient, DIDS-sensitive folate uptake was cis inhibited (greater than 90%) by reduced folate analogues: dihydrofolate (IC50 = 0.40 microM), folinic acid (IC50 = 0.50 microM), 5-methyltetrahydrofolate (IC50 = 0.53 microM), and (+)amethopterin (IC50 = 0.93 microM). In contrast, 10 microM (-)amethopterin had only a modest effect on folate uptake (18% inhibition) suggesting stereospecificity of the folate/OH- exchanger. The nonpteridine compounds which are transported by the folate carrier in L1210 leukemic cells (phthalate, thiamine pyrophosphate, and PO4(-3] did not inhibit jejunal folate uptake. Furthermore, folate uptake was not inhibited by SO4(-2) (4 mM) or oxalate (4 mM) thereby distinguishing this carrier from the previously described intestinal SO4(-2)/OH- and oxalate/Cl- exchangers. After BBM vesicles were loaded with 3H-folate, the initial velocity of 3H-folate efflux was stimulated by unlabeled folate in the efflux medium. The transstimulation of 3H-folate efflux by unlabeled folate was furosemide (or DIDS) inhibitable and temperature sensitive. Half-maximal stimulation of furosemide-sensitive 3H-folate efflux was observed with 0.25 +/- 0.05 microM unlabeled folate, a concentration similar to the Km for folate uptake. These data suggest that folate-stimulated 3H-folate efflux is mediated by the folate/OH- exchanger.(ABSTRACT TRUNCATED AT 250 WORDS)
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