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X. Zhang, A.M. Laties, C.H. Mitchell; Adenosine Protects Retinal Ganglion Cells from Cytotoxic Death following P2X7 Receptor Stimulation . Invest. Ophthalmol. Vis. Sci. 2003;44(13):5201.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To study the effect of ATP P2X7 receptor agonist BzATP and adenosine on retinal ganglion cells (RGCs). Methods: 1) Cell viability studies: RGCs were backlabled by injecting Fluoro-Gold dye into the superior colliculus of Long Evan rat pups on PD2-6. Retinas were dissociated from PD6-15 and plated onto poly-L-lysine coated coverslips. After culturing for 24 hours with the drugs added to the medium, fluorescent cells present in 40 fields on each coverslip were counted in a masked fashion. 2) Intracellular Ca2+ measurements: Unlabled RGCs grown on coverslips for 24 hours were loaded with 10µM fura-2 and Ca2+ levels in RGCs were measured ratiometrically using a fluorescent imaging system. Results: BzATP killed up to 30% of RGCs at a concentration of 50µM when incubated in mixed retinal culture for 24 hours. Cell loss was concentration-dependent and increased with 100 µM and 500 µM BzATP. Cell loss was reduced by a 30 min preincubation with adenosine (300µM-1mM) and co-incubation of adenosine with BzATP. BzATP produced large elevations in cell calcium which frequently remained elevated after BzATP removal. Adenosine itself did not affect Ca2+ levels but pre- and co-treatment did attenuate the BzATP-triggered elevations and reduced the sustained Ca2+ elevation. Conclusions: Stimulation of P2X7 receptors can elevate Ca2+ and kill RGCs. Adenosine can stop the P2X7-triggered Ca2+ overload and prevent cell death.
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