Bacterially synthesized folate in rat large intestine is incorporated into host tissue folyl polyglutamates.

Unlike mammalian tissues, certain intestinal microflora are capable of de novo synthesis of folate. To explore the availability of bacterially synthesized folate to the host organism, we used [3H] p-aminobenzoic acid (3H PABA) to label folate newly synthesized by the intestinal microflora. Labeled folates were isolated by affinity chromatography and identified by ion-pair HPLC. In this study [3H]PABA was injected into rat cecum to determine whether the [3H]folate synthesized by bacteria appeared in rat liver and other tissues. Rats were kept in sling suits to prevent coprophagy. Ion-pair chromatography of the purified liver folate demonstrated that bacterially derived [3H]folate was incorporated into all host liver-specific folate polyglutamates, mostly penta- and hexaglutamyl derivatives. Similar results were observed in kidney folates. These data provide direct evidence that some of the folate synthesized by the microflora in the rat large intestine is incorporated into the tissue folate of the host.