QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kownacki-Brown, P. A. Articles by Gregory, J. F. Search for Related Content PubMed PubMed Citation Articles by Kownacki-Brown, P. A. Articles by Gregory, J. F., III

Urinary Excretion of Deuterium-Labeled Folate and the Metabolite p-Aminobenzoylglutamate in Humans^1,2,3,4,

Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611-0370

Stable isotopic methods were employed to determine the proportion of ingested folate excreted as the metabolite p-aminobenzoylglutamate (pABG, free and N-acetyl) in urine. Adult male subjects (n = 7) were maintained on a 4.54 µmol/d (2 mg/d) folate saturation regimen. After 7 d, subjects were given a mixed oral dose containing 0.67 µmol (300 µg) each of bideuterofolic acid (d2) and tetradeutero-folic acid (d4). Urine was collected for the following 48 h and analyzed for folate and pABG. The extent of deuterium labeling of urinary folate and pABG was determined by gas chromatography-mass spectrometry. urinary total pABG excretion increased less than twofold as a result of the folate saturation, whereas urinary folate increased over 10-fold. Urinary d2 and d4 folates each contained 14–15% of the respective oral doses of labeled compounds, whereas urinary d2 and d4 pABG comprised only 0.98–1.15% of the labeled doses. Molar ratios (d2/d4) of excreted folate and pABG indicated that there was no in vivo isotopic discrimination between the labeled folates. Urinary pABG accounted for 5.1 ± 0.6% of total ingested folate, whereas labeled pABG was about 6.7–7.6% of the excretion of labeled compounds (i.e., labeled folate + pABG). This study indicated that pABG is not a major excretory product during folate supplementation, but its relative importance may increase in conditions of reduced folate nutriture.

KEY WORDS: • folate • stable isotope • humans • p-aminobenzoylglutamate

¹ Presented in part at the Annual Meeting of the Federation of American Societies for Experimental Biology, April 1992, Anaheim, CA [Gregory, J. F., Brown, P. A., Bailey, L. B. & Toth, J. P. (1992) Urinary excretion of deuterium-labeled folate and the metabolite p-aminobenzoylglutamate in human subjects. FASEB J. 6: A150 (abs.)].

² Supported by grant # 88-37200-3620 from the U.S. Department of Agriculture, Competitive Research Grants Program.

³ Florida Agricultural Experiment Station Journal Series no. R-02806.

⁴ The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

⁵ To whom correspondence should be addressed.

Manuscript received 18 November 1992. Revision accepted 5 February 1993.