Free radicals in rabbit retina under ocular hyperpressure and functional consequences

Area of Science:

• Ophthalmology
• Neuroscience
• Biochemistry

Background:

• Ocular ischemia, induced by high intraocular pressure, is linked to retinal oxidative stress and functional impairment.
• The specific oxygen-derived free radicals and their generation mechanisms during ocular ischemia remain unclear.

Purpose of the Study:

• To identify and characterize oxygen-derived free radicals produced in the retina during and after high intraocular pressure-induced ischemia.
• To correlate free radical generation with retinal function alterations.

Main Methods:

• Electron spin resonance (ESR) spin trapping using 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) in retinal microdialysates.
• ESR measurement of ascorbyl free radical-dimethyl sulfoxide (AFR-DMSO) complex to assess oxidative stress.
• Electroretinogram (ERG) recordings to evaluate retinal function.

Main Results:

• Superoxide dismutase-inhibitable DEPMPO/hydroxyl radical adducts were detected during the high intraocular pressure period.
• Oxidative stress levels, assessed by spin trapping and AFR-DMSO, did not increase during reperfusion.
• Free radical scavengers demonstrated functional protection against high intraocular pressure-induced ERG alterations.

Conclusions:

• Direct ESR measurements confirm the production of oxygen-derived free radicals in the retina during acute ischemia.
• This free radical generation is a likely cause of electroretinogram alterations observed under high intraocular pressure.
• The findings elucidate the biochemical mechanisms underlying retinal damage in ocular ischemia.