Expression of the facilitated glucose transporters (GLUT1 and GLUT3) by a choriocarcinoma cell line (JAr) and cytotrophoblast cells in culture

The expression of GLUT1 and GLUT3 mRNA and protein in human placental trophoblast-derived cells was investigated. A dividing choriocarcinoma derived cell line (JAr) was compared to differentiating cytotrophoblast cells, isolated from human term placenta, following 18 (mononucleate) and 66 h (multinucleate) in culture. JAr cells treated with 8-bromoadenosine, which inhibits growth and induces differentiation, were also studied. GLUT1 mRNA and protein expression were similar in the four groups of cells. However, GLUT3 mRNA expression was significantly higher (six- to sevenfold) in both control and 8-bromoadenosine-treated JAr cells compared to cytotrophoblast cells and was also significantly higher in untreated versus treated JAr cells. Western blotting showed that GLUT3 protein was undetectable in either cytotrophoblast cell groups, but was abundant in both groups of JAr cells. GLUT3 protein in JAr cells treated with 8-bromoadenosine was also significantly lower than in untreated JAr cells, in agreement with the mRNA data. We conclude that GLUT1 expression is unaffected by either growth or differentiation of trophoblast cells whereas GLUT3 expression is associated with dividing cells. We propose that in the placenta, GLUT3 may be involved in maintaining metabolic requirements of dividing trophoblast cells, rather than having a direct role in transport of glucose to the fetus.