Absorption of Folic Acid From the Small Intestine of the Rat

Burgen, A. S. V.; Goldberg, Neil

doi:10.1111/j.1476-5381.1962.tb01194.x

Cited by 38 publications

(22 citation statements)

References 12 publications

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“…FA has been thought to be absorbed from the upper gut (3,4), but defective F A absorption was observed in some patients with diseases of the distal ileum (5,6). On the other hand, concerning the mechanism of FA absorp tion, it has been suggested that active transport system may play a main role (7,8), but it is not established yet and is still controversial.…”

mentioning

confidence: 99%

The Clinical and Experimental Studies on the Metabolism of Folic Acid Using Tritiated Folic Acid

Yoshino

1968

J. Vitaminol

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confidence: 99%

The Clinical and Experimental Studies on the Metabolism of Folic Acid Using Tritiated Folic Acid

Yoshino

1968

J. Vitaminol

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“…TURNER and HUGHES [54], SPENCER and Bow [48], and YOSHINO [61] have shown evidence in favor of the passive absorption of folic acid in the rat and hamster. BURGEN and GOLDBERG [5], HERBERT and SHAPIRO [28], and HEPNER [25] have shown evidence in favor of the active transport of folic acid in the proximal small intestine of the rat. HEPNER'S data suggest that the folate absorption is active in the jejunum and passive in the ileum of the rat.…”

Section: Discussionmentioning

confidence: 99%

“…The mechanism and site of folic acid absorption has been studied in man [4,26,55] and in animals [5,14,25,28,48,54,61]. Most of the investigators have shown that folic acid is better absorbed in the proximal small intestine [25,26,28,55,61].…”

Section: Discussionmentioning

confidence: 99%

Folate Metabolism in Newborns and during Early Infancy: I. Absorption of Pteroylglutamic (Folic) Acid in Newborns

Shojania

Hornady

1970

Pediatr Res

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ExtractFolic acid (PGA) absorption (40 ,«g/kg of body weight) was studied in normal newborns and adults using Lactobacillus casei and Streptococcus faecalis microbiological assays for folate determination. The PGA was given orally or intramuscularly to the subjects after either saturating their tissues with folate or without prior saturation of their tissues. Without prior saturation of the tissues the folic acid absorption curves in newborns were much lower than those found in adults (figs. 1 and 2). Saturation of the tissues of the newborns with folic acid, prior to administration of the oral test dose, raised the absorption curves of the folic acid, but these were still lower than those seen in adults (fig: 5). The folate curve of the newborns after an intramuscular test dose of PGA was also lower than that observed in adults (fig. 3); however, after saturating the tissues of the newborns with folic acid, the folate curve became comparable to that of the unsaturated adults ( fig. 4).After the oral test dose, newborns excreted a much smaller percentage of the administered dose in their urine than did the adults (table II). When the tissues in newborns were saturated with folic acid, however, the excretion of folate in the urine became comparable to that of unsaturated adults (table II) These data indicate that: 1) plasma clearance of folate in newborns is more rapid than that in adults and that large saturating doses of folic acid are needed to reduce this clearance rate; and 2) the folate absorption curve in the newborn is lower than in the adult. With the criteria set for adults, this could be interpreted as evidence of impaired folate absorption in newborns. The proper interpretation of the data indicates, however, that folate absorption by newborns is slower than seen in adults and that the net absorption is comparable to that of adults. SpeculationIn newborns, the absorption curve for orally administered folate is lower than in adults. Our study indicates that this is due to the slower absorption of folates and more rapid tissue uptake of folates by newborns. Further studies should be carried out to investigate the absorption of folate conjugates which are the main forms of folate found in food, to determine how much of the folate in food is available to newborns and small infants, and to evaluate the need for supplementary folate in small infants. SHOJANIA and HORNADY 413

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“…MIost studies of intestinal folate absorption in man and animals (1)(2)(3)(4)(5)(6)(7)(8) have centered around pteroylmonoglutamic acid (PGA)' which is stable and readily available. Less than 10%, , of dietary folate, however, is PGA (9).…”

Section: Introductionmentioning

confidence: 99%

Intestinal Folate Absorption

Olinger¹,

Bertino²,

Binder³

1973

J. Clin. Invest.

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A B S T R A C T These studies were designed to determine whether pteroylmonoglutamic acid (PGA) at physiologic concentrations is transported across the small intestine unaltered or is reduced and methylated to the circulating folate form (5-methyltetrahydrofolate PGA concentration: at 7, 20, and 2,000 nM, 44%, 34%, and 2%, respectively, was converted to 5-AMeFH4. In contrast, less than 4% of the folate transferred across ileal mucosa was 5-MeFH4 when the initial mucosa concentration was 20 nM. Specific activity of dihydrofolate (DHF) reductase, the enzyme responsible for converting PGA to tetrahydrofolic acid, was measured in villus homogenates and was significantly greater in the jejunum than in the ileum. 1,000 nM methotrexate (MTX), a DHF reductase inhibitor, markedly inhibited PGA conversion to 5-MeFH4 by the jejunum.Studies of transmural flux, initial rate of mucosal entry (influx) and mucosal accumulation (uptake) of folate were also performed. Although MTX did not alter the influx of PGA, MTX decreased jejunal mucosal uptake but increased transmural movement. Trans-

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Absorption of Folic Acid From the Small Intestine of the Rat

Cited by 38 publications

References 12 publications

The Clinical and Experimental Studies on the Metabolism of Folic Acid Using Tritiated Folic Acid

The Clinical and Experimental Studies on the Metabolism of Folic Acid Using Tritiated Folic Acid

Folate Metabolism in Newborns and during Early Infancy: I. Absorption of Pteroylglutamic (Folic) Acid in Newborns

Intestinal Folate Absorption

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