The effect of dietary lipids on the toxicity of methylmercury (MeHg) was investigated in experimental MeHg poisoning of rats.
Three groups of weanling rats, with 8 to 12 animals in each group, were fed on vitamin E-deficient diet containing 10% beef tallow, cod liver oil or corn oil respectively for 5 weeks and the amount of plasma TBA (Thiobarbituric acid)-reactants, expired ethane and pentane and the level of oxidative hemolysis were measured every week. After the 5 weeks of feeding, the animals were subcutaneously injected with 10mg/kg of MeHg per day for consecutive 5 days. Body weight and crossing phenomenon of hind limbs were checked every day and the amounts of expired ethane and pentane were also measured every 3 days. Results obtained are as follows.
1. At the end of 5 weeks on the diets, the plasma level of TBA-reactants, the amounts of expired ethane and pentane and the level of oxidative hemolysis were significantly higher in the groups fed cod liver oil or corn oil than in the group fed beef tallow, indicating that the lipid peroxidation might be stimulated and the erythrocyte membrane might be weakened in the rats fed vitamin E-deficient diets containing much polyunsaturated fatty acids.
2. Both the latent period for the crossing phenomenon of hind limbs and the survival period after the dose of MeHg were shorter in the groups fed cod liver oil or corn oil than in the group fed beef tallow, suggesting that the former groups might be more susceptible to the toxicity of MeHg than the latter.
3. The amount of ethane or pentane decreased for several days after initial injection of MeHg, and thereafter remarkably increased in agreement with the appearance of the manifest signs of MeHg poisoning in either groups of rats, suggesting that increased production of these hydrocarbons might be a response to the impairment of the defense mechanism against lipid peroxidation by MeHg poisoning rather than MeHg itself.
