Folic acid, 5-methyl-tetrahydrofolate and 5-formyl-tetrahydrofolate exhibit equivalent intestinal absorption, metabolism and in vivo kinetics in rats

• Published in: The Journal of nutrition Vol. 122; no. 9; pp. 1847 - 1854
• Main Authors: Bhandari, S.D. (University of Florida, Gainesville, FL), Gregory, J.F. III
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Nutritional Sciences 01.09.1992
• Subjects: ABSORCION; ABSORPTION; ACIDE FOLIQUE; ACIDO FOLICO; Animals; Biological and medical sciences; Biological Availability; DISPONIBILIDAD DE NUTRIENTES; ELEMENT NUTRITIF DISPONIBLE; Enzymes. Coenzymes. Vitamins. Pigments; Feces; Folic Acid - pharmacokinetics; Folic Acid - urine; Fundamental and applied biological sciences. Psychology; Intestinal Absorption; Kinetics; Leucovorin - pharmacokinetics; Leucovorin - urine; Male; Metabolisms and neurohumoral controls; RAT; RATA; Rats; Tetrahydrofolates - pharmacokinetics; Tetrahydrofolates - urine; Tritium; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Excretion; Molecular form; Rat; Rodentia; Gut; Vitamin; Bioavailability; Folic acid; Folate; Vertebrata; Mammalia; Absorption; Body compartment; Kinetics
• ISSN: 0022-3166; 1541-6100
• DOI: 10.1093/jn/122.9.1847

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 (t 1/2) of 0.11-0.12 d, whereas the t 1/2 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