Corneal endothelial abnormalities in the Royal College of Surgeons rat.

For the first time, we report the pathologic changes in the corneal endothelium of the Royal College of Surgeons (RCS) rat with inherited retinal dystrophy. In the 26-day-old RCS rat, scanning electron microscopy (SEM) revealed several mushroom-like microvilli on the endothelial surface. Transmission electron microscopy (TEM) showed vesicle-like structures that corresponded to the mushroom-like microvilli. However, in the 90-day-old RCS rat, the corneal endothelium had numerous filamentous microvilli, and half of the endothelial cells had cytoplasmic edema, which was also observed by TEM. In the 180-day-old RCS rat, SEM showed numerous slender microvilli on the corneal endothelium. TEM showed thinning of the cells, with loss of cytoplasm and organelles, and thickening of Descemet's membrane. These endothelial changes could be caused by the toxic substances derived from the degenerating photoreceptor cells in the dystrophic retina.