Effects of L-cysteine, L-cysteine derivatives and ascorbic acid on lead excretion in rats

Urinary and fecal excretion of lead in rats were compared after intravenous administration of L-cysteine and a number of its derivatives. In terms of increasing total lead excretion, L-cysteine ethyl ester was about half as effective as D-penicillamine, whereas L-cysteine and all other derivatives tested were only marginally effective. Interestingly, L-cysteine ethyl ester appeared to increase lead depletion mainly through biliary excretion. This compound may, therefore, have lower renal toxicity than other chelating agents which promote lead excretion principally by increasing urinary elimination. Dietary supplements containing 1% cysteine, 1% ascorbic acid or 1% of both substances did not dramatically increase lead elimination.