Low levels of inorganic mercury damage the corneal endothelium

The effect of inorganic mercury on the integrity of the endothelium of isolated bullfrog (Rana catesbeiana) corneas was examined by spectrophotometric analysis of corneal uptake of the vital stain Janus green, and by both transmission (TEM) and scanning (SEM) electron microscopy. The uptake of Janus green by the endothelium is dose related between 1.0 and 30.0 microM HgCl2. The effect of mercury is not altered by changes in external calcium concentration, nor is it influenced by the calcium ionophore A23187, indicating that inorganic mercury damages the corneal endothelium through a mechanism which does not involve competition with external calcium or interaction with calcium channels. TEM and SEM demonstrate significant ultrastructural damage to the endothelium exposed to inorganic mercury, including cellular swelling, increased vacuolization, focal denuding of Descemet's membrane, and diminished integrity at the intercellular junctions.