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Y. Njie, O. Y. N. Bongmba, C. A. Opere, M. McKoy, S. E. Ohia; Regulation of Mammalian Retinal Neurotransmitter Function by Hydrogen Sulfide: Role of Cyclic AMP. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2005.
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Since H2S has been reported to induce the production of cyclic AMP in primary cultures of rat brain cells (Kimura, BBRC 267: 129, 2000), the present study examined the role of this nucleotide in retinal response to NaHS.
The methodology employed in this study is essentially the same as described by Ohia et al. (JOPT 11:73, 1995). Briefly, isolated bovine and porcine neural retinae were incubated in oxygenated Krebs buffer solution containing flurbiprofen (3 µM) and isobutylmethylxanthine (2 mM) for 30 minutes. After incubation, tissues were exposed to NaHS or forskolin at different time intervals (5 - 40 mins) and tissues were homogenized, boiled for 20 mins and then centrifuged. The supernatant from each sample was analyzed for cyclic AMP using an EIA kit purchased from Cayman Chemicals, Ann Arbor, MI.
In isolated bovine and porcine retinae, NaHS (10 nM - 100 µM) produced a time-dependent increase in cyclic AMP concentrations over basal levels which reached a maximum at 20 mins. For instance, in bovine retinae, NaHS (1 µM) caused a significant (P<0.001) increase of 200%, 300% and 200% at 5 mins, 20 mins and 40 mins, respectively. As positive control, forskolin (10 µM) also produced a 5-fold increase in cyclic AMP over basal levels. NaHS elicited a concentration-related increase in cyclic AMP concentrations in both bovine and porcine retinae. In bovine retinae, 10 nM, 1 µM and 100 µM NaHS caused 50%, 200% and 300% increase in cyclic AMP over basal levels, respectively.
We conclude that H2S can increase the production of cyclic AMP in mammalian retinae, an action that may account, at least in part, for the observed inhibitory action of this gas on neurotransmitter function in the retina.
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