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Madhura S. Kulkarni, Ya Fatou Njie-Mbye, Ikechukwu Okpobiri, Min Zhao, Catherine A. Opere, Sunny E. Ohia; Regulation Of Endogenous Hydrogen Sulfide Production In Isolated Bovine Retina By Carbon Monoxide And Nitric Oxide. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5669.
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© ARVO (1962-2015); The Authors (2016-present)
Nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) are endogenously produced in mammalian tissues and can serve as gaseous neuromodulators. Evidence from our laboratory shows that H2S is endogenously produced in various tissues of the bovine eye, a response that is enhanced in the presence of H2S donors and blocked by inhibitors of enzymes that synthesize this gas. In this study, we investigated the interaction between CO, NO and H2S in isolated bovine retinae.
H2S concentrations in bovine retinae were measured using a well established spectrophotometric method. Briefly, retinae were homogenized in a mixture of zinc acetate and borate buffer followed by addition of N, N-dimethyl-p-phenylenediamine and ferric chloride. Samples were incubated at 37°C and centrifuged at 5000g. The absorbance of the resulting solution was measured at 670 nm and H2S concentration was calculated against a calibration curve of standard H2S (10-750 µM). Effects of NO synthase inhibitor, L-nitroarginine methyl ester (L-NAME), NO donor, sodium nitroprusside (SNP), heme oxygenase inhibitor, zinc protoporphyrin (ZnPP-IX) and heme oxygenase inducer, hemin were tested in isolated bovine retinae.
L-NAME (100 µM and 300 µM) significantly enhanced (p< 0.05) the basal endogenous production of H2S whilst SNP (100 µM) had no significant effect on the level of this gas. The CO inhibitor, ZnPP-IX (1 µM and 10 µM) significantly enhanced (p< 0.05) the endogenous production of H2S whereas the CO inducer, hemin (2 µM and 20 µM) significantly attenuated (p< 0.05) the endogenous production of H2S.
We conclude that inhibitors of NO and CO production can unmask an inhibitory action of these gases on endogenous H2S biosynthesis in bovine isolated retina. Demonstration of a possible interaction between NO, CO and H2S in the mammalian retina, opens up new opportunities for a better understanding of the physiological and pharmacological role of these gaseous mediators in the eye.
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