Physiological effects of tert-butyl hydroperoxide on the rabbit corneal epithelium

Rabbit corneas were mounted atraumatically into an automatic voltage clamp apparatus for the determination of open circuit potential difference and short circuit current. The corneal tissue was bathed on both sides with a Ringer solution, continuously stirred and aerated. After a minimum 1 hour equilibration, a single dose of tert-butyl hydroperoxide (t-BHP) (0.1 mM to 2 mM) was administered to the tear-side solution. This led to an immediate fall in epithelial potential difference and short circuit current. The electrical conductance tended to be subnormal during the peak response. The initial decreases were partially reversed, but even after several hours the majority of corneas sustained abnormal levels of potential difference and conductance. Administration of 2 mM t-BHP to the tearside solution led to an immediate fall in epithelial thickness to -25% of baseline. This was followed by large-amplitude oscillations in corneal epithelial thickness which were sustained over several hours. We conclude that prolonged exposure of the perfused rabbit cornea to small tearside amounts of t-BHP are capable of modulating the electrophysiologic integrity of the corneal epithelium. T-BHP exceeding 1 mM in the tears could compromise the non-catalase dependent antioxidant defense mechanisms in rabbit corneal epithelium.