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Charlotte E. Remé, Uwe Wolfrum, Cornelia Imsand, Farhad Hafezi, Theodore P. Williams; Photoreceptor Autophagy: Effects of Light History on Number and Opsin Content of Degradative Vacuoles. Invest. Ophthalmol. Vis. Sci. 1999;40(10):2398-2404.
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purpose. To investigate whether regulation of rhodopsin levels as a response to
changed lighting environment is performed by autophagic degradation of
opsin in rod inner segments (RISs).
methods. Groups of albino rats were kept in 3 lux or 200 lux. At 10 weeks of
age, one group was transferred from 3 lux to 200 lux, another group was
switched from 200 lux to 3 lux, and two groups remained in their native
lighting (baselines). Rats were killed at days 1, 2, and 3 after
switching. Another group was switched from 3 lux to 200 lux, and rats
were killed at short intervals after the switch. Numbers of autophagic
vacuoles (AVs) in RISs were counted, and immunogold labeling was
performed for opsin and ubiquitin in electron microscopic sections.
results. The number of AVs increased significantly after switching from 3 lux to
200 lux at days 1 and 2 and declined at day 3, whereas the reverse
intensity change did not cause any increase. Early time points after
change from 3 lux to 200 lux showed a significant increase of AVs 2 and
3 hours after switching. Distinct opsin label was observed in AVs of
rats switched to 200 lux. Ubiquitin label was present in all
investigated specimens and was also seen in AVs especially in 200-lux
conclusions. Earlier studies had shown that an adjustment to new lighting
environment is performed by changes in rhodopsin levels in ROSs.
Autophagic degradation of opsin or rhodopsin may subserve, at least in
part, the adaptation to abruptly increased habitat illuminance by
removing surplus visual pigment.
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