ABSTRACT
Chlorpyrifos [CPF] is a widely used organophosphorous insecticide that induces toxic effects in man and animal through its inhibitory action on acetyl choline esterase enzyme. The present work aimed to evaluate the toxic effect of chlorpyrifos on the function and structure of the suprarenal gland and to investigate the possible protective effect of silymarin antioxidant against such toxicity. The study included twenty four adult male rats they were equally divided into four groups as follows: a control group [n=6] received the oral vehicle only [corn oil], a Silymarin group [n=6] received Silymarin in a dose of 6mg/kg b. w orally twice weekly for four weeks, the intoxicated group [n=6] received CPF 5mg/kg b. w, orally twice weekly for four weeks and the protection group [n=6] receivied silymarin orally 6mg/kg b. w. half an hour after chlorpyrifos, administration in a dose of 5mg/kg b. w. orally twice weekly for four weeks. By the end of the experiment, estimation of the following biochemical parameters was done: plasma choline esterase enzyme activity level, serum cholesterol, serum cortisol and serum testosterone. The suprarenal gland was examined by the light microscope using routine H and E stain and chromaffin stain reaction as well as by the Transmission Electron Microscope. The measured biochemical parameters showed significant variation in CPF group compared to the control. The chlorpyrifos intoxicated group revealed affection of the cells of the suprarenal cortex and medulla with variable degrees of degenerative changes. The protection group showed improvement of the levels of the biochemical parameters with partial restoration of the normal histological features of the suprarenal structure compared to the CPF intoxicated group. Accordingly, it was proved that silymarin is a reliable antioxidant that could protect against the toxic effect of chlorpyrifos on the suprarenal gland