The metabolism of pteroylglutamic acid by the rat

Guggenheim, K.; Halevy, S.; Neumann, Hannah; Usieli, Varda

doi:10.1042/bj0620281

Cited by 10 publications

(1 citation statement)

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“…These results must be viewed with caution, since both groups used very large doses (up to 175mg for humans) and Silverman et al (1956) used formic acid, which, we have shown, reacts with 5-CH3-H4PteGlu to give 5,10-CH=H4-PteGlu. Low conversions into urinary citrovorum factor activity have been reported for PteGlu when given orally (Anderson et al 1960;Broquist, Stokstad & Jukes, 1951;Baker et al 1965;Oji, Wada & Yoshida, 1951) or subcutaneously (Guggenheim, Halevy, Neumann & Usiel, 1956). More recently McLean & Chanarin (1966 have shown no activity for P. cerevi8iae.…”

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The urinary excretion of orally administered pteroyl-l-glutamic acid by the rat

Blair

Dransfield

1971

Biochemical Journal

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1. The urinary excretion of folates after oral administration of [2-(14)C]pteroyl-l-glutamic acid was studied by assaying the radioactivity in the urine and in materials purified and characterized by t.l.c. 2. Radioactivity excreted was 6.8, 5.9 and 30.7% of the oral dose in the first 24h after doses of 3.1, 32 and 320mug/kg respectively. 3. Extensive decomposition of urinary folates to pteroyl-l-glutamic acid was prevented by antioxidants or collection of urine frozen. 4. At the three dosages, two major and one minor radioactive compounds were isolated. One of the major metabolites was 5-methyltetrahydropteroylglutamic acid. The others were unidentified but were not pteroylglutamic acid, 7,8-dihydro-, 5,6,7,8-tetrahydro-, 5- or 10-formyl-tetrahydro-, 5,10-methylidyne-tetrahydro-, 5-formimidoyl-tetrahydro-, 5,10-methylene-tetrahydro-, 5-methyltetrahydro-pteroylglutamic acid, nor any decomposition products of these compounds formed during isolation. Labelled unconjugated pteridines were absent. 5. Labelled pteroyl-l-glutamic acid was displaced by oral administration of unlabelled pteroyl-l-glutamic acid (1.6mg/kg) when given 3.5h after, but not when given 24h after the labelled dose. 6. The results show that orally administered [2-(14)C]pteroyl-l-glutamic acid is absorbed without metabolism and is then metabolized into naturally occurring tetrahydro-folates. 7. These findings are discussed with reference to previous work.

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confidence: 99%