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Hypoxia inhibits rhodopsin regeneration in the excised mouse eye
S E Ostroy1, C G Gaitatzes, A L Friedmann
1Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-7801.
Purpose:
The goal of this study was to evaluate the effect of oxygen deprivation on rhodopsin regeneration in the excised mouse eye.
Methods:
A new preparation for studying rhodopsin regeneration with a superfused excised albino mouse eye was developed. The preparation exhibits multiple regenerations after moderate bleaches (15%-20%) and is sensitive to the composition of the perfusate, allowing reversible testing of conditions. A variety of protocols were used to evaluate the effect of hypoxia. The major experiments varied the timing of the decreased oxygen relative to the illumination: Decreasing the oxygen (1) before the illumination, (2) immediately after the illumination, or (3) some time after the illumination, after half of the rhodopsin had regenerated. Elevated concentrations of extracellular glucose also were used for certain experiments.
Results:
Regardless of protocol, at low levels of oxygen no rhodopsin regeneration was observed. The effects were reversible, however, and decreased oxygen for up to 3 hr did not diminish the ability of the eye to regenerate rhodopsin after restoration of the oxygen and a subsequent bleach.
Conclusions:
Low levels of oxygen eliminated rhodopsin regeneration in the excised eye. The effect could not be offset by high levels of glucose, illumination, or other conditions known to reduce the dependence of photoreceptors on aerobic respiration.