Water transport across isolated term human amnion

Summary

The hydrodynamic permeability of normal term human amnion is measured using pressure-driven bulk flows. The permeability coefficient is found to vary widely, variations between tissues taken from different subjects being significantly greater than those from samples taken from one subject. No correlation is observed between this coefiicient and either tissue thickness or the diffusional permeability coefficient measured using tritiated water; it is, however, found to be very sensitive to epithelial damage.

The results indicate that the bulk transport of water through amnion is largely controlled by the amniotic epithelium alone. This contrasts with water diffusion which is a function of total membrane thickness. The two permeability coefficients cannot therefore be employed to formulate an equivalent pore model of the whole tissue. An equivalent pore model of the epithelial layer only is considered and the results assessed in the light of other evidence bearing on the structure of amnion. It is concluded that the epithelial layer is intersected by a large number of pores with radius 10 to 30 Å, and a smaller number of much broader pores.