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Jenaye Robinson, Leah Bush, Olivia Nguyen, Catherine A Opere, Sunny E Ohia, Ya Fatou Njie-Mbye; ROLE OF BIOSYNTHETIC ENZYMES AND PROSTAGLANDINS ON HYDROGEN SULFIDE LEVELS IN PORCINE OCULAR ANTERIOR SEGMENT OUTFLOW MODEL. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6413.
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© ARVO (1962-2015); The Authors (2016-present)
In a previous study, we reported that H2S donors can reduce intraocular pressure in normotensive rabbits presumably by increasing aqueous humor (AH) outflow through the trabecular meshwork. In the present study, we investigated the contribution of endogenous H2S and the role of intramurally-generated prostaglandins in the observed increase in AH outflow facility in an ex vivo porcine ocular anterior segment model.
Porcine ocular anterior segment explants were perfused with Dulbecco’s Modified Eagle’s Medium maintained at 37° C and gassed with 5% CO2 and 95% air under an elevated pressure of 15 mmHg for four hours. Perfusates from the anterior segment explants were collected and immediately assayed for H2S content using the well-established Methylene Blue assay. In some experiments, explants were perfused with an inhibitor of H2S biosynthesis [aminooxyacetic acid (AOAA, 30-100 µM) and α-ketobutyric acid (KBA, 1 mM)] or with cyclooxygenase (COX) inhibitors [flubiprofen (30 µM and indomethacin (10 µM)]. The concentration of H2S was also measured in the AH (as a positive control), and at normal perfusion pressure of 7.35 mmHg in the absence of AOAA and COX inhibitors.
Elevating perfusion pressure from 7.35 to 15 mm Hg significantly (p < 0.001) increased H2S concentrations from 0.4 ± 0.1 to 67.6 ± 3.6 nM/µg protein. As a reference value, the H2S concentration in the AH was 1.5 ± 0.2 nM/µg protein. In the presence of AOAA (30 µM) or KBA (1 mM), the effects of elevated pressure on H2S levels were significantly (p < 0.001) reduced from 67.6 ± 3.6 to 5.7 ± 0.3 nM/µg protein and 4.9 ± 0.8 nM/µg, respectively. Likewise, flurbiprofen (30 µM) and indomethacin (10 µM) attenuated the elevated pressure-induced increase in H2S levels.
We conclude that the elevated perfusion pressure-induced increase in H2S concentrations is dependent upon endogenous biosynthesis of H2S and on intramurally-produced prostaglandins in the porcine anterior segment explants.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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