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Titolo:
EVIDENCE FOR THE EXISTENCE OF A CARRIER-MEDIATED FOLATE UPTAKE MECHANISM IN HUMAN COLONIC LUMINAL MEMBRANES
Autore:
DUDEJA PK; TORANIA SA; SAID HM;
Indirizzi:
UNIV ILLINOIS,DEPT MED,MED RES SERV 600 151,VET AFFAIRS MED CTR,820 SDAMEN AVE CHICAGO IL 60612 WESTSIDE VET AFFAIRS MED CTR CHICAGO IL 60612 UNIV CALIF IRVINE,VET AFFAIRS MED CTR LONG BEACH CA 90822
Titolo Testata:
American journal of physiology: Gastrointestinal and liver physiology
fascicolo: 6, volume: 35, anno: 1997,
pagine: 1408 - 1415
SICI:
0193-1857(1997)35:6<1408:EFTEOA>2.0.ZU;2-X
Fonte:
ISI
Lingua:
ENG
Soggetto:
NA+ TRANSPORT; VESICLES; INTESTINE; EXCHANGE; JEJUNUM;
Keywords:
FOLATE TRANSPORTER; HUMAN LARGE INTESTINE; PLASMA MEMBRANES; TRANSPORT KINETICS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
27
Recensione:
Indirizzi per estratti:
Citazione:
P.K. Dudeja et al., "EVIDENCE FOR THE EXISTENCE OF A CARRIER-MEDIATED FOLATE UPTAKE MECHANISM IN HUMAN COLONIC LUMINAL MEMBRANES", American journal of physiology: Gastrointestinal and liver physiology, 35(6), 1997, pp. 1408-1415

Abstract

Colonic bacteria synthesize significant amounts of folate. The current studies were undertaken to examine the presence of a possible folatetransporter and its characterization in apical membranes of the humancolon. Apical membrane vesicles were purified from mucosal scrapings of proximal organ donor colons using a differential centrifugation anddivalent cation precipitation technique. [H-3]folate (PteGlu) uptake was measured by a rapid filtration technique. Our results demonstrate that [H-3]PteGlu uptake into these vesicles 1) was significantly increased with decreasing pH of the incubation buffer, 2) was markedly inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and -acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid but; not by acetazolamide, amiloride, bumetanide, furosemide, and diphenyl 2-carboxylic acid, 3) was sensitive to temperature and osmolarity of the incubation medium, 4) was inhibited by structural analogs methotrexate and 5-methyltetrahydrofolate, 5) exhibited trans-stimulation phenomenon, 6) was potential insensitive, and 7) exhibited saturation kinetics with an apparent Michaelis constant for PteGlu of 8.2 +/- 2.4 mu M and a maximal enzyme reaction rate of 19.8 +/- 2.9 pmol.mg protein(-1).10 s(-1). Studies on distal colonic membranes also demonstrated the presence of a folate transporter with similar kinetic characteristics. These results demonstrate the existence of a pH-dependent, DIDS-sensitive, electroneutral carrier-mediated mechanism for folate absorption in the human colon.

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Documento generato il 17/01/21 alle ore 16:28:11