The metabolic fate of (2-14C)folic acid and a mixture of (2-14C)- and (3',5',9-3h)-folic acid in the rat.

The metabolism of [2-14C]folic acid over 13 days and a mixture of [2-14C]- and [3',5',9-3h]-folic acid in rats over a 6-day period is described. Both 14C and 3H are excreted in urine over the 6-day period, but 3H and 14C are only detectable in faeces for 2 days. A breakdown product of folic acid labelled with 3H only was found in some urine samples, but no metabolite corresponding to the part of the molecule containing 14C was detected. These experiments show that in the whole animal a substantial portion of orally administered folic acid undergoes scission shortly after administration [Blair Biochem. J. (1957) 68, 385-387] and that the retained folates are a shortage form for folate monoglutamates.