Folate Binding in Animal Plasma

Abstract

Plasma from pig, sheep, goat, cattie, horse, rabbit, dog, rat, guinea pig, and chicken was examined for the presence of specific binders for folic acid. It was found that only pig plasma contains unsaturated avid specific binders of folic acid. The maximum binding capacity of pig plasma for folic acid was found to be 14.0–26.5 ng/ml of plasma. These binders have a lower affinity for other folates and folate analogues. They are partly saturated by endogenous folates and they move electrophoretically in veronal buffer, pH 8.6, in an area including β-globulin and most of the γ-globulin fraction. Specific binders of folic acid with high binding capacity were also found in one female sheep out of the 16 tested.