Abstract
1. The effects of rat plasma and chicken pancreas have been appraised concerning their role in releasing bound folate from rat liver and spleen slices in vitro. Net changes in folate concentration of the bathing solution have been determined by bacteriologic assay employing L. casei as the test organism.
2. Both rat plasma and chicken pancreas extract enhance the release of folate from liver slices in comparison with saline controls. Rat plasma was as effective in liberating bound folate from liver as a 1:25 dilution of conventionally-prepared chicken pancreas extract. The evidence suggests that a considerable portion of liver folate exists in an insoluble form which is bound to cellular structures.
3. Mature red cells appeared to be impermeable to high concentrations of natural folate released from liver.
4. Spleen slices released folate to the supernatant fluid when incubated with chicken pancreas extract, although at levels approximately one-tenth as great as liver slices. When spleen slices were incubated for short periods with plasma, evidence was obtained favoring a flux of folate into surviving cells.
