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Angelino J. Cariello, Gabriela F. de Souza, Rodrigo A. Souza-Lima, Elisa S. Ferreira, Marcelo G. de Oliveira, Ana L. Hofling-Lima; Corneal Permeation Of Nitric Oxide Donors In Porcine Corneas. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3244.
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To determine the corneal permeation of two nitric oxide (NO) donors, S-nitrosoglutathione (GSNO) and S-nitroso-N-acetylcysteine (SNAC) and their active metabolites (nitrite and nitrate), through freshly isolated pig cornea.
For in vitro study, nine corneas excised from porcine eyes were divided in three groups (GSNO, SNAC and control) and were individually sandwiched between two compartments of a Franz-type diffusion cell. The compartment in contact with the corneal epithelium was filled with GSNO or SNAC at concentration of 40mM and buffer solution was placed in the endothelial compartment. The control experiments received buffer solution in both compartments. Sequential 0.175 ml aliquots were taken every 30 minutes (total of 6 samples) from the endothelial compartment to analyze the permeation rate. For ex vivo study, eighteen intact porcine eyes were divided in three groups and received fifty microliters of a 40mM concentration solution of GSNO, SNAC, or buffer solution (control group). Every 30 minutes, a sample of aqueous humor (0.3 ml) was collected of one eye (total of six samples). The concentration of NO metabolites was estimated both in the in vitro and ex vivo experiments by chemiluminescence and the concentration of GSNO and SNAC were estimated by Ultra Performance Liquid Chromatography.
After 3 hours, in the in vitro tests GSNO was not detectable in all aliquots but SNAC showed an ascendant logarithmic curve. Nitrite and nitrate displayed an ascendant time-dependent curve different from control in both GSNO and SNAC analyses (p<0.05). SNAC showed greater NO metabolites permeability than GSNO in all experiments. Ex vivo and in vitro experiments showed similar results.
The permeation study indicated that SNAC and active NO metabolites can cross the intact cornea. These results suggest that ocular topic instillation of S-nitrosothiols used for therapeutic purposes (such as ocular antimicrobial or antihypertensive action) can reach the anterior chamber.
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