Degradation of annular gap junctions of the equine hoof wall.

Annular gap junctions interiorized within cells of the stratum spinosum of the coronary border of the equine hoof were degraded by two methods. Some were autophagocytized and some appeared to fuse with lysosomes to form heterophagosomes. Structural changes of partially degraded annular gap junctions included increased density of the enclosed cytoplasm, formation of filamentous or membrane-like material within the annular gap junction, and disruption of the circular or oval profile of the gap junction. The annular gap junctions are apparently incorporated into the fully keratinized cells of the stratum corneum.