8-bromo-cyclicAMP stimulates glucose transporter-1 expression in a human choriocarcinoma cell line

Facilitative glucose transporter-1 (GLUT1) is abundant in trophoblast cells and is responsible for glucose transport in the placenta. However, the cha nge in GLUT expression in human placenta upon trophoblast differentiation r emains to be clarified. Therefore, we first examined the localization of GL UT1 and GLUT3 using human first-trimester chorionic villi. We found that GL UT1 and GLUT3 were mainly localized to syncytiotrophoblast and cytotrophobl ast cells respectively. We analyzed whether placental GLUT1 and GLUT3 expre ssion changes during differentiation using a human choriocarcinoma (BeWo) c ell line which is known to show functional and morphological differentiatio n in response to cAMP in culture. Treatment of BeWo cells with 8-bromo-cycl icAMP (8-bromo-cAMP) increased the level of hCG secretion and induced cell fusion leading to the formation of large syncytia. Treatment of BeWo cells with 8-bromo-cAMP also resulted in a significant increase in glucose uptake on days 2-3 of culture. The stimulating effect of 8-bromo-cAMP on glucose uptake was concentration dependent. Northern and immunoblot analyses reveal ed that the levels of mRNA and protein of GLUT1, but not of GLUTS, were sig nificantly increased by 8-bromo-cAMP. These findings suggest that 8-bromo-c AMP stimulates GLUT1 expression with differentiation in BeWo cells.