Antioxidant Effects of Silymarin on Ischaemia- Reperfusion Injuries of the Rabbit Retina

Retinal ischaemia is known as the main reason of blindness in disease such as closed angle glaucoma and diabetes. The aim of this study was to investigate the protective effect of silymarin in injuries induced by ischaemic-reperfusion of rabbit eyes. Thirty male adult New Zealand white rabbits were divided into three groups of ten animals each. All animals in the two experimental groups underwent bilateral common carotid ligation for 60 min. After 48 hours reperfusion all animals were sacrificed. Silymarin-treated group received 250 mg/kg of silymarin 48 h before surgery, placebo-treated group received same volume of normal saline as experimental group I, without any medication and control group was non-ischaemic and untreated. After processing, retinal histology samples were investigated by electron microscopy. The concentration of lipid peroxides in retinas was measured. Histology results of this experiment revealed that in the reperfusion groups, the group that received no treatment had major signs and silymarin group had minor signs of pathology. The loss of outer segments, scattered and disorganised inner segments were observed in placebo-treated group, but in silymarintreated group the outer segment was normal and inner segments were organised. On the other hand, some pyknotic, condensed, and karyorrhexis nuclei in the outer nuclear layer were obvious in placebo-treated group. Measurement of concentration of lipid peroxides in the retina also showed a significant decrease in malondialdehyde (MDA) level in silymarin-treated group.