Transferrin in cultured human term cytotrophoblast cells: synthesis and heterogeneity.

Transferrin (Tf) mRNA was recently demonstrated in rat and mouse placental tissue. Rat placental cells were shown to secrete transferrin. The cell type with which Tf mRNA was associated was not investigated. We therefore studied the ability of immunopurified human term cytotrophoblast cells in culture to synthesize Tf, by means of pulse-label experiments with 35S-methionine and report that these cells do synthesize Tf. Tf mRNA was demonstrated in the cell lysates by means of RT-PCR. Tf isolated from cytotrophoblast and syncytiotrophoblast cells was shown to be different from both maternal and fetal serum Tf with respect to the distribution of isoforms as demonstrated by means of iso-electric focusing. The iso-electric points were found at lower pH values (pH 5.0-5.4), compared to the iso-electric points of maternal and fetal serum Tf, suggesting a higher degree of sialylation and glycan chain complexity.