Folic acid, 5-methyl-tetrahydrofolate and 5-formyl-tetrahydrofolate exhibit equivalent intestinal absorption, metabolism and in vivo kinetics in rats.
The intestinal absorption and in vivo kinetics of (6S)-[3H]-5-methyl-tetrahydrofolate (5-methyl-H4folate), (6S)-[3H]-5-formyl-H4folate and [3H]folic acid were investigated to determine whether inherent differences exist in the overall bioavailability of these folates in rats. Adult rats (n = 9 per group) were given an intragastric dose of the appropriate folate (50 pmol/100 g body wt) in 50 mmol/L ascorbate (pH 7). Each compound underwent nearly complete absorption within 8 h, and there was no significant difference in the excretion kinetics in relation to the form of folate administered. A biphasic pattern of excretion was observed over the following 8 d. Both urine and feces were important excretory routes. The rapid phase of total isotopic excretion (urinary and fecal) exhibited a half time (t1/2) of 0.11-0.12 d, whereas the t1/2 of the slower phase was 13.4-15.9 d. Isotopic distributions and the pattern of labeled folates in urine and tissues were similar regardless of the form administered. These results indicate that the bioavailability of orally administered folic acid, 5-methyl-H4folate and 5-formyl-H4folate is equivalent in rats under the conditions of this study.
Bhandari
S D
SD
Food Science and Human Nutrition Department, University of Florida, Gainesville 32611-0370.
Gregory
J F
JF
D000818:Animals; D001682:Biological Availability; D005243:Feces; D005492:Folic Acid / Q000493:pharmacokinetics* / Q000652:urine; D007408:Intestinal Absorption; D007700:Kinetics; D002955:Leucovorin / Q000493:pharmacokinetics* / Q000652:urine; D008297:Male; D051381:Rats; D013763:Tetrahydrofolates / Q000493:pharmacokinetics* / Q000652:urine; D014316:Tritium
D013763:Tetrahydrofolates; D014316:Tritium; D005492:Folic Acid; D002955:Leucovorin; C005984:5-methyltetrahydrofolate