The influence of high maternal plasma glucose levels, and maternal blood flow on the placental transfer of glucose in the guinea pig.

Abstract

The relationship between maternal and fetal plasma glucose concentrations and placental glucose transfer has been studied in the anaesthetised guinea pig. The fetal circulation of the placenta, left ‘in situ’, was perfused through the umbilical arteries, after removal of the fetus, with a low molecular weight dextran, containing physiological salts and 100 mg/100 ml glucose. The maternal plasma: fetal perfusate concentration ratio of antipyrine, infused at a constant rate into the maternal circulation, was used to monitor the changes in maternal placental blood flow. — As the maternal plasma glucose was increased from 100 to 450 mg/100 ml the perfusate concentration followed, but at a slower rate. No further increases in perfusate concentration occurred after the maternal plasma level exceeded 450 mg/100 ml which suggests a maximum capacity of the placental membrane to transport glucose, analogous to that observed for the renal tubule and blood brain barrier. — The transfer rates of glucose from the fetal to the maternal circulation were similar to those in the opposite direction, with the same linear relationship to the transplacental gradients. Transfer, in either direction across the placental membrane, was reduced when the maternal placental blood flow was impaired, as indicated by a maternal: fetal antipyrine ratio below 0.6.