Change in structure of tight junctions between epithelial cells in the uterine tube of the rat during early pregnancy.

Freeze-fracture electron microscopy has been used to study tight junctions of epithelial cells in the rat fallopian tube. At oestrus, junctions were found to consist of strands parallel to the surface whereas at day 6 of pregnancy, junctions were deeper and extensively interconnected. We consider the involvement of ovarian hormones and the cross-tissue significance of our findings.