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Light-evoked oxygen responses in the isolated toad retina
L M Haugh-Scheidt1, E R Griff, R A Linsenmeier
1Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208, USA.
Experimental Eye Research
|July 1, 1995
Summary
Light exposure decreases retinal oxygen consumption by slowing the photoreceptor sodium-potassium (Na+/K+) ATPase pump. Lowering sodium reveals a faster, cyclic GMP-mediated increase in oxygen use.
Area of Science:
- Ophthalmology
- Neuroscience
- Cellular Physiology
Background:
- Retinal oxygen consumption changes with light stimuli.
- The role of sodium-potassium (Na+/K+) pumping in this response is not fully understood.
Purpose of the Study:
- To investigate transient changes in retinal oxygen consumption during light stimulation.
- To elucidate the mechanisms underlying light-evoked oxygen utilization in the retina.
Main Methods:
- Utilized double-barreled microelectrodes to simultaneously measure oxygen and voltage near photoreceptor inner segments in toad retina.
- Recorded light-evoked oxygen responses in normal and low extracellular sodium ([Na+]) conditions.
- Administered a phosphodiesterase inhibitor (3-isobutyl-1-methyl-xanthine) to assess cyclic GMP involvement.
Main Results:
- In normal [Na+], light increased retinal oxygen tension, indicating decreased oxygen utilization.
- In low [Na+], light decreased oxygen tension, showing increased utilization primarily due to cyclic GMP.
- The Na+/K+ ATPase pump's effect on oxygen consumption was found to be slower than the cyclic GMP-mediated response.
Conclusions:
- Light-evoked oxygen consumption in the retina is modulated by both Na+/K+ ATPase activity and cyclic GMP pathways.
- The Na+/K+ ATPase contributes a slower, dominant effect on oxygen consumption under normal physiological conditions.
- Cyclic GMP-mediated oxygen utilization is a faster, yet typically masked, component of the light response.