Intestinal folate absorption

Abstract

A B S T R A C T Intestinal absorption of the monoglutamate form of the principal dietary and circulating folate compound, 5-methyltetrahydrofolic acid (5-MTHF), was studied in the rat utilizing a synthetic highly purified radiolabeled diastereoisomer. Chromatography confirmed that the compound was not altered after transfer from the mucosa to the serosa. Accumulation against a concentration gradient was not observed in duodenal, jejunal, or ileal segments at 5-MTHF concentration from 0.5 to 500 nmoles/liter. Unidirectional transmural flux determination also did not indicate a significant net flux. Mucosal to serosal transfer of 5-MTHF was similar in all segments of the intestine and increased in a linear fashion with increased initial mucosal concentrations. Further, no alteration in 5-MTHF transfer was found when studied in the presence of metabolic inhibitors or folate compounds.These results indicate that 5-MTHF is not absorbed by the rat small intestine by a carrier-mediated system and suggest that 5-MTHF transfer most likely represents diffusion. INTRODUCTIONThe mechanism of folate' absorption in man and experimental animal is not established. Both the paucity of

Uptake and Reduction of Radioactive Folate by Everted Sacs of Rat Small Intestine

“…However, the site of this metabolic transformation was in dispute, because the participation of the liver could not be excluded [20-221. Reduction and methylation of PteGlu in systems in vitro was also reported [7,14] but the findings were not confirmed [16].…”

Factores Determinantes Del Estado Nutricional Del Folato Y El Rol De La Variante Genética C677t De La Enzima Metilen Tetrahidrofolato Reductasa -MTHFR-

“…Además, se ha descrito un sistema absorción por difusión tras la ingesta de dosis farmacológicas (10). Al interior del enterocito las formas oxidadas de folato son reducidas mediante la incorporación de átomos de hidrógeno en el anillo pteridina para obtener el tetrahidrofolato (THF), se transfieren grupos de un carbono en las posiciones 5 y 10 del ácido pteróico, formando diferentes coenzimas necesarias para procesos metabólicos específicos (1).…”