OPSIN SYNTHESIS IN THE C57BL 6-MIVIT/MIVIT MOUSE MODEL OF RETINAL DEGENERATION/

The capacity of photoreceptor cells to synthesize opsin was evaluated in a newly-described mouse model of retinal degeneration, the C57BL/6- mi(vit)/mi(vit). The mi(vit)/mi(vit) mouse loses photoreceptor cells a t a rate of about one row per month beginning at 8 weeks, ROS are seve rely disrupted at 4 months, RPE is unevenly pigmented. Retinas of affe cted and control mice ages 4, 6, 8, 12, 16, 20, 24, 28, 32 and 52 week s were incubated for 2 hours in medium containing [H-3] leucine. Homog enates of retina samples were subjected to SDS-PAGE using disc gels. T he gels were sliced and counted by scintillation. The incorporation of [H-3] leucine into opsin was compared with its incorporation into oth er retinal proteins. During the early time points studied, mi(vit)/mi( vit) retinas incorporated proportionately similar amounts of [H-3] leu cine into opsin versus other retinal proteins as did controls. At 12 w eeks, the percentage was about 80% and it continued to decline over th e succeeding weeks studied. By 1 year, the proportion of leucine incor porated into opsin versus other proteins was only about 23% the amount incorporated in controls. The results of the present study suggest th at the mi(vit)/mi(vit) photoreceptor cells are able to synthesize opsi n and the gradual decline in synthetic ability follows the gradual los s of cells and is not correlated with the disruption of ROS.