Inhibition of nitric oxide synthesis in corneas in storage media

The nitrate/nitrite content in storage media was determined after nitric oxide synthase inhibition by adding 400 microl of 100 mm N(G)-monomethyl-l-arginine (LMMA) to four chambers of Optisol GS corneal storage media, each containing one viable human cornea. The companion corneas in storage media without LMMA served as controls. Four hundred microlitre aliquots obtained at baseline (day 0) and at one-day intervals for 20 more days for both groups were analyzed for nitrate and nitrite (breakdown products of nitric oxide) concentration levels using a spectrophotometric method based on the Greiss reaction. Average nitrate/nitrite concentrations, statistically analyzed using a polynomial random coefficients model, showed a statistically significant marked reduction in the levels of nitrate and nitrite accumulation in the study chambers as compared to control chambers for days 1-20(P < 0.001) There was also a reduction in the accumulation rate of nitrate and nitrite concentrations, as compared to controls (P < 0.05) until around day 8 when the differences in rates were no longer statistically significant. The progressive increase in nitrate and nitrite accumulation in corneal storage media can be blunted by the addition of a nitric oxide synthase inhibitor. Given the toxic free radical properties of nitric oxide, corneas in storage awaiting transplantation may benefit from having a nitric oxide synthase inhibitor added to storage media.