Distribution of Carotenoids and Protective Effects of Zeaxanthin on Retina of Ayu Sweetfish (Plecoglossus altivelis).

Abstract

Ayu sweetfish (Plecoglossus altivelis) is a diurnal freshwater fish that are surface swimmers and active under broad and short wavelength-dominated light. Biochemical analyses have shown that the ayu fish have abundant carotenoids including zeaxanthin in their integuments. Although zeaxanthin plays an important role in the physiological function of the retina, the amount and location of zeaxanthin in the ayu eye have not been accurately determined. In this study, circular dichroism spectral data and chiral high-performance liquid chromatography analysis showed that zeaxanthin was the primary carotenoid in the ayu eye, and the eye had the highest carotenoid content compared to those in the integuments, subcutaneous fat, and digestive tract. Interestingly, zeaxanthin in the ayu eyeball was expressed in the photoreceptor layer and near the retinal pigmented epithelium. In vitro assays showed that zeaxanthin could protect photoreceptors and retinal pigmented epithelial cell lines against the oxidative stress induced by exposure to L-buthionine-(S,R)-sulfoximine/glutamate. These findings indicate that zeaxanthin plays protective roles against oxidative stress in the vision of wild ayu.