Effects of Elevated Umbilical Venous Pressure on Fluid and Solute Transport Across the Isolated Perfused Human Placental Cotelydon

Abstract

Everyone who has perfused the placenta of the guinea pig, rat or rabbit, has observed that the venous outflow rate decreased when the umbilical outflow pressure was elevated. This observation implies that in the placentae of these species, elevation of the umbilical venous pressure promotes a significant volume flow from the perfused umbilical side of the placenta to the maternal circulation. The phenomenon has been described in more detail in the placenta of the guinea pig (Dancis et al., 1962), under conditions of in situ perfusion of the umbilical circuit and in the isolated dually perfused preparation (Leichtweiss and Schröder, 1977). Dancis and coworkers observed that water flux from the fetal to the maternal side of the placenta was greatly increased when the umbilical outflow pressure was elevated to about 20 cm H₂O, and that labeled albumin and erythrocytes, which had been added to the umbilical perfusion fluid, could readily be detected in the maternal circulation. In the experiments of Leichtweiss and Schröder, increasing the umbilical venous pressure caused a net fluid movement from the fetal to the maternal side without any observable evidence for sieving off the albumin molecules. Electron microscopy of the perfused tissue, using horseradish peroxidase as a tracer, demonstrated that wide bag-shaped channels open in the placental trophoblast when the umbilical outflow pressure is increased (Kaufmann et al., 1982).