An ultrastructural study of microvascular inter-endothelial tight junctions in normal endometrium

To investigate changes in tight junctions between microvascular endothelial cells in normal endometrium.

A quantitative transmission electron microscopy study of changes in the number of tight junctions per microvessel, and widths and lengths of individual junctions at different phases of the menstrual cycle.

Two types of tight junctions were defined ("open" and "closed") which varied in the degree of separation between apposed plasma membranes of endometrial endothelial cells. Tight junction density was greater in proliferative than secretory phases (p<0.02). The width and length measurements of individual tight junctions changed during menstruation.

The two types of tight junctional contacts and the changes in width and density may reflect variation in structure and function between adjacent endothelial cells. These junctions may have importance in the processes of implantation and menstruation.