Evidence for a specific transport of D-hexoses across the human term placenta in vitro

Abstract

Isolated cotylidons of human term placentas are perfused artificially on the fetal and maternal side. The relative transfer rates of radioactive labelled D-glucose, L-glucose, D-mannose and D-mannitol across the placenta are measured and the inhibition of these transports by phloretin is studied: 1. Transfer rates of D-glucose and D-mannose exceed that of L-glucose about 1.5-4 times. 2. Phloretin (10(-3) mol/l) decreases the transports of D-hexoses, whereas the transport of L-GLUCOSE REMAINS UNAFFECTED. 3. If the concentration of D-glucose is increased, the transport of D-mannose is inhibited competitively. 4. L-glucose and D-mannitol equal in transfer rates. These results show, that D-hexoses cross the human placenta by a specific carrier and by simple diffusion.