para-acetamidobenzoylglutamate is a suitable indicator of folate catabolism in rats.
The amount of biologically active folate excreted in the urine corresponds to a small fraction of the recommended dietary allowance, suggesting that a large amount of folate is excreted as its catabolites. A strategy of assessing folate requirement by measuring the daily urinary levels of products of folate catabolism depends on the demonstration of an exclusive mechanism of breakdown as well as a suitable marker of the catabolic process. Rats were given [3H] and [14C]folic acid by gastric intubation daily for 10 d to simulate normal dietary intake of the vitamin. Total urine was collected throughout this period as well as for the following 10 d. Reverse-phase HPLC of the radiolabeled urinary products revealed the presence of a variety of intact folates as well as products of C9-N10 scission of the folate molecule, pteridines, para-aminobenzoylglutamate and para-acetamidobenzoylglutamate. We detected no other N10-containing catabolites, nor did we find the oxidized folate derivative '4 alpha-hydroxy-5-methyltetrahydrofolate'. Of all the urinary folate metabolites, only para-acetamidobenzoylglutmate persisted at high levels up to 10 d after radiolabel treatment was withdrawn. We conclude that folate catabolism occurs exclusively through C9-N10 cleavage and that measurement of urinary para-acetamidobenzoylglutmate provides a suitable indicator of daily folate turnover.
Geoghegan
F L
FL
Department of Clinical Medicine, University of Dublin, Trinity College, Ireland.
McPartlin
J M
JM
Weir
D G
DG
Scott
J M
JM
D010129:4-Aminobenzoic Acid / Q000652:urine; D000818:Animals; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage / Q000378:metabolism* / Q000652:urine; D007441:Intubation, Gastrointestinal; D002955:Leucovorin / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013763:Tetrahydrofolates / Q000378:metabolism; D014316:Tritium; D062366:para-Aminobenzoates
D002250:Carbon Radioisotopes; D013763:Tetrahydrofolates; D062366:para-Aminobenzoates; C023730:Acedoben; D014316:Tritium; D005492:Folic Acid; D002955:Leucovorin; D010129:4-Aminobenzoic Acid; C005984:5-methyltetrahydrofolate