Unidirectional transport across cultured ovine amniotic epithelial cell monolayer

Objective: To determine whether ovine amniotic cells in monolayer culture exhibit unidirectional transport. Methods: Permeability of ¹⁴C-inulin was measured in two directions across ovine amniotic cells grown to confluence on cell culture inserts. Results: Permeability was 0.69 + 0.17 (SE) μl/min/cm² from the top of the insert where the cells were attached to the bottom and 0.11 + 0.02 μl/min/cm² in the reverse direction (P < 0.001). Permeability was similar in the two directions for chorionic cells and umbilical vein endothelial cells. Addition of vascular endothelial growth factor did not alter permeability. Conclusions: Transcellular transport in ovine amniotic monolayers is directionally specific. The transport ratio of 6.2:1 for ¹⁴C-inulin is comparable to the in vivo ratio of 4.7:1 for the ovine intramembranous pathway and is consistent with passive diffusion in both directions and vesicular transport in one direction across the monolayer at 5.2 times the rate of passive diffusion.