Comparison between the unsaturated plasma folate binder and in vivo labelled plasma folate binder.

Endogenous plasma folate binder denuded of folate by dialysis at pH 3, subsequently bound more methylfolate than folic acid, in contrast with the minor unsaturated plasma binder which bound folic acid in preference to methylfolate. On Sephadex DEAE-A50 chromatography 14C-CH3H4PteGlu bound to acid-denuded endogenous binder, eluted like the endogenous binder-radioactivity, labelled in vivo after oral 14C-CH3H4PteGlu. It is suggested that the endogenous plasma folate binder is not identical with the unsaturated binder.