Vitamin A induced Changes in Ocular Tissue Lipid Peroxidation and Antioxidant Enzymes Activities of Rabbits in Cadmium Toxicity

Abstract

The study investigated the effect of oral administration of vitamin A on antioxidant enzyme {superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (Gln Px)} activities and malondialdehyde (MDA) levels in rabbits exposed to ocular cadmium (Cd). Twenty New Zealand rabbits weighing between 1670 – 1810g were assigned to four groups of animals containing 5 rabbits each. The rabbits were placed in wire meshed cages and allowed to acclimatize to laboratory conditions for two weeks with free access to food and water throughout the study. One group of rabbits which served as control, was fed with chow and administered with eye drops of 2mgkg -1 body weight Cd (as 3CdSO 4 .8H 2 O). The remaining two groups of animal treatments were carried out in accordance with the principles of laboratory animal care. The study lasted for four weeks and the cornea, retina and lens of the eyes recovered for assay. The result revealed that the significant reduction (P<0.05) in the weight of rabbits exposed to cadmium was improved by administration of Vitamin A. However, 500mg vitamin A reduced feed intake. The observed accumulation of cadmium in the eye tissues which resulted in increased levels of malondialdehyde (oxidative damage) was ameliorated to levels comparable to control when treated with Vitamin A supplements. Some antioxidant enzymes activities in the eye tissues were also significantly (P<0.05) reduced with exposure to cadmium when compared with control. Vitamin A improved the activities of these enzymes particularly with lens SOD and CAT. The effects of vitamin A was dose dependent with the rabbits given 500mg vitamin showing remarkable recovery of the SOD and CAT activities to levels which compared favourably with those observed in the control. The study therefore reveals that Vitamin A supplement at different doses can enhance the antioxidant enzyme capacity in cadmium toxicity.