Characterization of the folate receptor in human molar placenta.
We have characterized a high-affinity folate receptor in human molar placenta tissue. Radioligand binding exhibited characteristics typical of other high-affinity folate binding proteins. Those included, positive cooperativity, a tendency to increased binding affinity with decreasing receptor concentration, a slow ligand dissociation at pH 7.4 becoming rapid at pH 3.5, and inhibition by folate analogues. The folate receptor cross-reacted with antibodies against human milk folate binding protein, e.g. the syncytothrophoblastic layer of molar placenta tissue sections showed strongly positive immunostaining. The gel filtration profile contained two radioligand-bound peaks (25 and 100 kDa), however, with considerable overlap. Only a single band of 70 kDa was seen on SDS-PAGE immunoblotting. The folate receptor in placental tissue may play a crucial role in the transfer of folate from maternal circulation to the fetus.
Department of Clinical Chemistry, Horsens Hospital, Denmark.
J
J
Holm
S I
SI
Hansen
C W
CW
Nichols
M
M
Høier-Madsen
P E
PE
Helkjaer
D000931:Antidotes / Q000494:pharmacology; D002352:Carrier Proteins / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D058973:Folate Receptors, GPI-Anchored; D005493:Folic Acid Antagonists / Q000494:pharmacology; D006801:Humans; D006828:Hydatidiform Mole / Q000737:chemistry*; D015151:Immunoblotting; D007150:Immunohistochemistry; D002955:Leucovorin / Q000494:pharmacology; D008727:Methotrexate / Q000494:pharmacology; D010920:Placenta / Q000737:chemistry*; D011247:Pregnancy; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D014327:Trophoblasts / Q000737:chemistry; D014594:Uterine Neoplasms / Q000737:chemistry*
D000931:Antidotes; D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D005493:Folic Acid Antagonists; D011956:Receptors, Cell Surface; D002955:Leucovorin; D008727:Methotrexate