Transthyretin-thyroid hormone internalization by trophoblasts.

Normal fetal neurological development depends on a regulated supply of maternal thyroid hormone (TH). We have previously demonstrated that transthyretin (TTR) a TH binding protein, is synthesized, secreted and internalized by trophoblast cells and may provide a route for the transfer of TH from mother to fetus. Our objective was to determine if a member of the low-density lipoprotein receptor family mediates TTR or TTR-TH internalization. TTR-TH internalization by JEG-3 cells is reduced in the presence of receptor associated protein (RAP) or albumin suggesting that TTR-TH is internalized through an LDL-receptor dependent endocytic process.