EFFECTS OF DIETARY ALPHA-TOCOPHEROL AND BETA-CAROTENE ON LIPID-PEROXIDATION INDUCED BY METHYL MERCURIC-CHLORIDE IN MICE

Exposure of male CBA mice to methyl mercuric chloride, CH3HgCl, (10-40 mg/1 in drinking water) for 2 weeks resulted in dose-related Hg deposition and enhanced lipid peroxidation in liver, kidney and brain. Mice were fed well-defined semisynthetic diets containing different levels of alpha-tocopherol (10, 100 or 1000 mg/kg) or beta-carotene (1000, 10000 or 100000 IU/kg) for four weeks, two groups on each diet. The concentrations of alpha-tocopherol and beta-carotene used corresponded to deficient, normal and high levels. During the last two weeks, one group on each diet was given 40 mg CH3HgCl/l of drinking water. High dietary alpha-tocopherol protected against CH3HgCl induced hepatic lipid peroxidation, whereas the alpha-tocopherol deficient diet further enhanced CH3HgCl induced hepatic lipid peroxidation. Similar, though statistically non-significant effects occured in the kidneys, alpha-Tocopherol did not protect against CH3HgCl induced lipid peroxidation in the brain. Excess dietary beta-carotene further enhanced CH3HgCl induced lipid peroxidation in liver, kidney and brain. CH3HgCl significantly decreased the activity of total glutathione peroxidase (T-GSH-Px) and Se-dependent glutathione peroxidase (Se-GSH-Px) in the kidneys in all dietary groups. High dietary alpha(-tocopherol enhanced the activity of Se-GSH-Px in liver and kidney compared to the activity in mice fed the normal level of alpha-tocopherol. This occured in mice exposed to CH3-HgCl as well as in unexposed mice, and the difference between CH3HgCl exposed and unexposed mice was not diminished. High dietary a-tocopherol increased the activity of both Se-GSH-Px and T-GSH-Px in the brain of CH3HgCl-exposed mice. The dietary level of beta-carotene did not affect the activity of the two enzymes in the organs investigated.