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Christian Grimm, Charlotte E. Remé, Pascal O. Rol, Theodore P. Williams; Blue Light’s Effects on Rhodopsin: Photoreversal of Bleaching in Living Rat Eyes. Invest. Ophthalmol. Vis. Sci. 2000;41(12):3984-3990.
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purpose. To determine whether blue light induces photoreversal of rhodopsin
bleaching in vivo.
methods. Eyes of anesthetized albino rats were exposed to either green (550 nm)
or deep blue (403 nm) light, and the time course of rhodopsin bleaching
was determined. Rhodopsin was isolated from whole retinas by detergent
extraction and measured photometrically. To inhibit photoreversal of
bleaching, rats were perfused with 70 mM hydroxylamine
(NH2OH), a known inhibitor of photoreversal. To determine
whether blue-absorbing, photoreversible photoproducts were formed,
rhodopsin was bleached to near completion with green light and then
exposed to blue light. Finally, experimental results were simulated on
a computer by means of a simple, three-component model involving a
long-lived photoreversible photoproduct.
results. Photoreversal of bleaching in blue light occurs in vivo as evidenced by
the following: In the absence of NH2OH,
bleaching of rhodopsin by blue light was slow and complex. In the
presence of NH2OH, however, blue light bleached rhodopsin
very fast with a simple, pseudo–first-order kinetic. A long-lived
bleaching intermediate produced by green light exposure was
photoreversed to rhodopsin by exposure to blue light. The
three-component computer model, invoking a blue-absorbing,
photoreversible, long-lived intermediate accurately described the data.
conclusions. Because of the instantaneous, nonmetabolic regeneration of rhodopsin by
the process of photoreversal of bleaching, blue light exposure permits
the absorption of large numbers of photons by rhodopsin and by a
photoreversible intermediate of bleaching in vivo. These data may have
an important impact on resolving mechanisms of blue light–mediated
damage to the retina.
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