TROPHOBLASTIC GIANT-CELLS OF THE MOUSE PLACENTA CONTAIN CALBINDIN-D-9K BUT NOT THE VITAMIN-D-RECEPTOR

The effects of vitamin D deficiency on the ontogeny of calcium-binding proteins (CaBPs) and the vitamin D receptor (VDR) in the placenta and yolk sac of the mouse were examined. Maternal vitamin D status did no t affect the time of appearance of CaBP-D-9k (9 kDa) in the yolk sac e ndoderm or trophoblastic giant cells (TGCs) of the placenta. VDRs were undetectable in TGCs and yolk sac endoderm, but were present in the i ntraplacental yolk sac. Since yolk sac endoderm and TGCs contain CaBP but not VDR, it is unlikely that CaBP synthesis and/or activity in the se cells is controlled by vitamin D. The TGCs, therefore, may be invol ved in vitamin D-independent transplacental transfer of calcium.