Effect of high salt loading on the retina of adult male rats with special reference to aquaporin 1: a histological and immunohistochemical study

Background In the retina, glial cells control ionic concentrations by mediation of transmembrane water fluxes through aquaporin (AQP) water channels. The risk factor of a high-salt diet on renal and cardiovascular systems is pretty well known. However, it is not yet known whether a high-salt diet alone can affect the retina. Aim of the work The aim of this study was to determine whether a high-salt diet alone can induce changes in the retina and whether it may be accompanied by changes in the expression and immunolocalization of water channel aquaporin1 (AQP1). Materials and methods Forty-two adult male albino rats were used. They were divided into three equal groups. Group I served as the control group. Rats in group II were administered 2 ml of a high-salt solution (8% NaCl concentration) once daily by means of a gastric tube. Group III was the recovery group. Retinal tissues were collected and examined by means of light and electron microscopy. Immunohistochemical analysis using AQP1 and glial fibrillary acidic protein (GFAP) antibodies was performed and the results were statistically analyzed. Results The retina of rats given a high-salt diet (group II) displayed obvious disorganization of the outer segment of photoreceptors, together with cytoplasmic vacuolations in the cells of the inner nuclear and ganglionic layers. Furthermore, significant increase in AQP1 and GFAP immunoexpression was detected. In the recovery group (group III) the retinae of some rats regained their normal histological appearance, whereas others failed to do so. Conclusion High salt loading might alter glial cell-mediated water transport through AQP1 channels in the retina.