Effect of lead on erythrocytic antioxidant defence, lipid peroxide level and thiol groups in calves.

Fifteen crossbred male calves were exposed to lead for a period of 28 days orally at the dose rate of 7.5 mg of lead acetate as 0.75 per cent solution kg(-1)body weight to study its effect on erythrocytic antioxidant defense, lipid peroxide level and thiol groups. Five calves were given no treatment and served as unexposed controls. Blood samples were collected before exposure to lead and thereafter at weekly intervals (ie. on day 7, 14, 21 and 28). Erythrocyte haemolysate (10 per cent) was prepared and analysed for lipid peroxide level, activity of Superoxide dismutase (SOD) and catalase. Total, protein-bound and non protein-bound thiol groups were also measured. Exposure to lead significantly (P < 0.05) reduced the erythrocytic SOD activity by day 7 and it remained lower until day 21 followed by a marginal increase on day 28. Catalase activity declined after an initial compensatory rise on day 7. Erythrocytic lipid peroxide level was recorded to be significantly (P < 0.05) higher by day 21 and 28 of exposure. Total, protein-bound and non protein-bound -SH content of erythrocytes declined. It was concluded that oral exposure of lead reduced the erythrocytic thiol content and antioxidant defence indicating possible role of free radicals in pathogenesis of lead toxicity.