Purpose: The purpose of the study was to quantify nitric oxide release by human corneal buttons in storage media over time.
Methods: Group 1 consisted of six chambers of Optisol GS corneal storage media, each containing a viable human corneal button with an attached scleral rim (unsuitable for transplantation), sampled at 1-day intervals for at least 17 days (range, 17-28 days). Group 2 consisted of 34 chambers of Optisol GS media, each used to store a corneal button for penetrating keratoplasty, sampled immediately after each surgery. An unused vial of Optisol GS storage medium was sampled daily for 17 days to serve as a background medium control. The total amount of nitrite and nitrate in each sample was determined by a spectrophotometric method based on the Griess reaction.
Results: Data from the daily sampling in group 1 showed that nitrite and nitrate concentrations in storage media containing human corneas increase from a baseline level (beginning at the time the corneas are placed in the media) to an equilibrium concentration of 2.77 microM in a mean time of 6.15 days. Seventy-six percent of the data points from group 2 fell within the 80% predictive interval derived from group 1. No nitrite or nitrate was detected in background medium control samples.
Conclusion: The progressive increase in nitrite and nitrate in corneal storage media over time suggests that nitric oxide is continuously released by corneas during storage before transplantation. Given the toxic free radical properties of nitric oxide, corneas in storage media may be subjected to the cumulative toxic effects of nitric oxide.