Freeze-Etching of Intercellular Junctions of Mouse Liver

The tight junction at the bile canniculus of mouse liver contains a packed hexagonal particle array in the intercellular space. This region has been identified in freeze-etch preparations revealing several additional structures. Mouse liver is fixed in 2% purified glutaraldehyde for 2 hours and infiltrated with 20% glycerine for 1/2 hour. Fixative and cryoprotective solutions are prepared in sodium-free Krebs-Ringer phosphate pH 7.2 to 7.4 and the solutions are oxygenated before use. Fixation and infiltration are conducted at room temperature prior to quick freezing in liquid propane. Freeze-etch replicas are produced with a modified simple freeze-etch device, cleaned with “Clorox”, washed with distilled water and examined unsupported on 300 mesh grids in a Seimens Elmiskop 1A. Two different views of the Plasmalemma are observed (Fig.1). The intercellular surface is identified by the hexagonal particle array. Outside the tight junction this surface has a dense randomly distributed particle population. Viewed from the intracellular surface a circumscribed area reflects the closer membrane apposition of the occluding junction.