Permeability of Ovine Amnion and Amniochorion to Urea and Water

Abstract

Permeability of ovine amnion and amniochorion to urea and water was measured in vitro at various gestational ages. Permeability of amniochorion was between 30 and 100% of that of amnion. Permeability of the membranes to water did not change with fetal age, whereas permeability of amnion to urea decreased from 1.548 ± 0.541 (49) 10^-4 cm·sec^-1 to 0.277 ± 0.339 (102) 10^-4 cm· sec^-1 as fetal age increased. There was a significant relationship between the permeability of the amnion to urea and the concentration of urea in the amniotic fluid. It was concluded that the decrease in membrane permeability to urea may be responsible in part for the increase in amniotic fluid urea concentration observed as gestation progresses.