Role of Serum Folate Binders in the Delivery of Folate to Tissues and to the Fetus

Abstract

Specific folate binding protein (FBP) and non-specific FBP were prepared from pooled serum from patients in late pregnancy. The 2 classes of folate binder were labeled with 75Se-selenofolate and injected into non-pregnant and pregnant rabbits. Selenofolate bound to specific FBP was delivered predominantly to the liver, in both pregnant and non-pregnant animals. Fetal tissue took up selenofolate from the non-specific FBP only. Specific FBP thus functions to deliver folate to stores and represents a storage pool of folate. The non-specific FBP are responsible for the delivery of folate to the fetus and probably also to sites of utilization.