COMPARATIVE IN-VIVO LEAD MOBILIZATION OF MESO-2,3-DIMERCAPTOSUCCINIC AND RAC-2,3-DIMERCAPTOSUCCINIC ACIDS IN ALBINO WISTAR RATS

Comparison of the racemic and meso forms of 2,3-dimercaptosuccinic aci d (DMSA) in lead mobilization from lead-loaded albino Wistar rats demo nstrates that the racemic form is significantly more effective in redu cing femur lead levels. After four oral doses at 0.5 mmol/kg, femur le ad levels were reduced to 87% of control values by meso-DMSA and to 50 % of control levels by rac-DMSA. Similarly, when the dose was increase d to 1.0 mmol/kg, femur lead levels were reduced to 69% of control lev els by meso-DMSA and to 45% of control levels by rac-DMSA. A similar p attern was found for renal lead levels. Brain lead concentrations were significantly lower in treated groups than in control groups, but no differences were found between rac- and meso-DMSA. Rac-DMSA is more so luble than meso-DMSA in acetonitrile, ethyl acetate, and ethyl ether. The partition coefficient of mc-DMSA in the n-octano/water system was found to be about 2.8. These results indicate that rac-DMSA deserves f urther attention as a possible substitute for meso-DMSA.