REGULATION OF TRANSFERRIN RECEPTOR EXPRESSION AND DISTRIBUTION IN IN-VITRO CULTURED HUMAN CYTOTROPHOBLASTS

During gestation the transplacental iron transport is very important t o the fetus. Iron uptake by the placenta can be studied in cultured cy totrophoblasts. The influence of culture time and human diferric trans ferrin on the number and distribution of transferrin receptors (TfRs) was investigated in human cytotrophoblasts. Cytotrophoblasts cultured for 2.5 h had few TfRs (0.28 pmol/mg protein). With time, total TfR am ounts increase (4.14 pmol/mg protein at 70 h). They increase to a high er level in cells cultured in iron-poor medium, indicating that iron h as an effect on the TfR synthesis/breakdown ratio. TfRs were distribut ed between two 'active'(located at the cell surface and intracellularl y) and one 'inactive'(located intracellularly) receptor pools. TfR dis tribution among these pools was modulated by culture time and iron. Tr ophoblasts regulated iron uptake by variation of number of surface TfR s via changes in total TfRs and redistribution of TfRs among the recep tor pools.