Freeze-fracture images of the zonula occludens in the mouse oviduct epithelium.

Freeze-fracture images of zonulae occludentes of the oviduct epithelium of adult mice were observed in the electron microscope. The structure of zonulae occludentes varies depending on the types of oviduct epithelial cells. Those between two secretory cells consist of 5--14 (9.2 +/- 2.0) strands interposed between the luminal and the lateral plasma membrane. The strands run irregularly making well developed anastomoses with one another. The tight junction between two ciliated cells consists of 4--14 (8.5 +/- 2.3) strands. Among them the upper 3--9 strands are unique in shape. The strands run regularly, compactly and parallel to the luminal surface and to each other with a few anastomoses. The distance between the adjacent strands is about 40 nm. Under this characteristic part several strands are very loosely distributed and run irregularly. The pattern of the strands in the zonula occludens between a secretory cell and a ciliated one resembles that between adjacent ciliated cells. The junction consists of 4--13 (8.3 +/- 2.0) strands. The characteristically dense and parallel arrangement of the strands demonstrated in this study is presumed to be related to the ciliary movement. All the zonulae occludentes in the mouse oviduct epithelium are "very tight" in type. No large gap junctions are seen in the mouse oviduct epithelium.