Changes in lactate dehydrogenase activity in bovine corneal stroma and epithelium in response to in vitro toxic challenges in the enucleated eye test.

Purpose: To assess whether changes in lactate dehydrogenase (LDH) activity, as a marker of cell damage, could be detected in corneal stroma and corneal epithelium after toxicity measurements using the enucleated eye test (EET).
Methods: The corneal surface of isolated bovine eyes was continuously wetted with commercial balanced salt solution (BSS) over 4 h at 37 degrees C and central corneal thickness (CCT) was measured. Initial 5-min challenges were made with dilute solutions of benzalkonium chloride (up to 0.032%) or NaOH (up to 0.4 M). The residual LDH activity in the corneal epithelium and corneal stroma were then assessed.
Results: Dose-dependent increases in CCT of up to 70% were measured. A strong correlation (r = -0.961) was found between increases in CCT and decreases in stromal LDH activity, but the correlation was much less (r = -0.512) for epithelial LDH activity.
Conclusions: LDH activity can be used as one marker for cell integrity in the corneal stroma and epithelium, although dose-dependent correlations may not be high.