The influence of
methionine supplementation on the efficacy of common antidotes to
lead poisoning,
calcium disodium ethylenediaminetetraacetate (CaNa2EDTA) and
D-penicillamine (DPA), was investigated in rats. The animals were given
lead acetate (0.1% in
drinking water) for 12 weeks and thereafter treated with CaNa2EDTA. DPA (0.3 mmol/kg, intraperitoneally), DL-
methionine (1.34 mmol/kg, intragastrically), or the combination of a
chelating agent and
methionine for 3 days. While
chelating agents enhanced the urinary excretion of Pb,
methionine increased the fecal excretion of Pb significantly. Treatment with the combination of a
chelating agent and
methionine did not potentiate the effect of each
antidote. However,
methionine supplementation increased the efficacy of both
chelating agents in reducing the hepatic and renal Pb burden but not the blood Pb level. The Pb-induced inhibition of blood
delta-aminolevulinic acid dehydratase activity and the increase in urinary excretion of
delta-aminolevulinic acid were reversed to a certain extent by CaNa2EDTA, DPA, and
methionine but the combination did not improve their individual performances. The beneficial effects of
methionine may be attributed to its ability to increase the bioavailability of
glutathione (GSH), useful in chelating Pb and counter-acting the toxic effects, as evidenced by restoration of the Pb-induced decrease in hepatic GSH level by treatment with
methionine.
Methionine may be useful as a supportive
therapy in chelation of Pb.