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Cytosohc extracts of trout and turkey erythrocytes were tested for their lmmunoreactlvlty with polyclonal and monoclonal antlbodles to retmal arrestm (S-antigen), a cytosohc protem of photoreceptor cells involved m the desensltlzatlon of rhodopsm After adsorption or lmmunoaffimty chromatography of the extracts, these antibodies specifically recognized a protem having a molecular weight slmdar to that of retinal arrestm Because the G-protem-medlated transduction systems, such as visual and P-adrenerglc systems, display a high degree of structural and functlonal homology, the presence of arrestm-hke protems m non-photosensltlve cells suggests that these protems are Involved m the transduction of chemical signals, with a possible role m receptor desensltlzatlon Arrestm, Retmal S-antigen, Erythrocyte, /%Adrenerglc transduction, Phototransductlon, (Trout, Turkey)

Progressive degeneration of retinal photoreceptor cells occurs in albino rats when exposed to continuous lighting. Three proteins involved in the phototransduction cascade were immunodetected in these cells after various durations of continuous illumination. We found that S-antigen (arrestin) and rhodopsin immunoreactivities persisted for 1-2 months during the degenerative process, whilst immunoreactivity of the alpha subunit of transducin totally disappeared between day 2 and day 4 of continuous light exposure. This suggests that continuous illumination could impair alpha-transducin synthesis, a possible causal factor of photoreceptor damage.

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