EVALUATION OF 3 ANTIDOTES ON ARSENIC TOXICITY IN THE COMMON EARTHWORM(LUMBRICUS-TERRESTRIS)

The common earthworm (Lumbricus terrestris) is being evaluated in our laboratories as a substitute for mice in metal toxicity studies. These two disparate species have enzymes in common, such as catalase, super oxide dismutase and glutathione-S-transferase. Also, worms respond sim ilarly to these rodents for selenium and nickel toxicity. Worms are le ss sensitive, however, to metal toxicity. In this study earthworms wer e challenged with three different arsenic compounds: arsenite, arsenat e and the vesicant phenyldichloroarsine (PDA). The median lethal dose for each arsenic compound was determined. The order of toxicity of the arsenic compounds to the worms was PDA > arsenite > arsenate (24 h LD (50) values were 189.5, 191.0 and 519.4 mu mol kg(-1), respectively). Individual mammalian dithiol antidotes, namely the sodium salt of 2,3- dimercapto-1-propanesulfonic acid (DMPS), meso-dimercaptosuccinic acid (DMSA) or 2,3-dimercapto-1-propanol (BAL), were injected into the wor ms 5 min after various doses of the arsenic compound were administered . The decreases in acute toxicity values were recorded. All three anti dotes protected the worms against arsenic toxicity with varying degree s of effectiveness. The protective action for the inorganic arsenic co mpounds was in the order DMPS > DMSA > BAL. For the organic arsenical, PDA, the most effective antidote was BAL.