Histological and immunohistochemical study on the effect of sodium iodate on the retina of adult male albino rat and the possible protective role of silymarin

Abstract

Background: Retinal degenerative diseases are induced by many environmental and genetic agents and may lead to permanent blindness. Induced retinal degeneration by sodium iodate (NaIO3) is widely used to study mechanism of retinal cell death. Silymarin are flavonoids which has powerful antioxidant effects.Aim of work: Study the effects of NaIO3 on the retina of adult male albino rat and possible protective role of silymarin.Material and methods: Forty adult male albino rats were used, they were divided equally to four groups: group I (control), group II (silymarin), group III (NaIO3) and group IV (silymarin and NaIO3). At end of experiment, retina of the whole groups was prepared for histological and immunohistochemical studies. Paraffin sections were stained by hematoxylin and eosin (H&E), Glial fibrillary acidic protein (GFAP), Caspase3 and inducible nitric oxide synthase (iNOS) immunostaining. Morphometric measurements were done and data was statistically analyzed.Results: H &E sections of GIII revealed thinning, disorganization and loss of most layers of retina. Degeneration of retinal pigmented epithelium, damage of photoreceptors, necrosis and loss of cells of outer, inner nuclear layers and ganglion cell layers were noticed. Loss of reticular appearance, thinning of outer and inner plexiform layers and congested blood vessels in many layers were detected. GFAP, Caspase3 and iNOS revealed strong positive immune reaction in this group. Group IV showed marked improvement of retina but some changes were still seen. Electron microscope (EM) and morphometric results confirmed light microscopic results.Conclusion: Sodium iodate has destructive effects on all layers of retina and preceding silymarin has protective role.