Chelation of lead by dimercaptopropane sulfonate and a possible diagnostic use
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Teresa Twarog and M. George Cherian
Department of Pathology, Health Sciences Centre, University of Western Ontario, London, Ontario N6A 5C1, Canada
The mobilization of lead (Pb) from Pb-exposed rats was examined following administration of dimercaptopropane sulfonate (DMPS). A dose-response study showed that the highest dose of DMPS (200 μmol/kg, ip) removed Pb from kidneys, liver, and bone, while the lower doses (25 and 50 μmol/kg) chelated Pb only from the kidneys. In experiments where DMPS was repeatedly injected to Pb-exposed rats, the maximum urinary excretion of Pb was observed within 24 hr after the first injection, with little effect in subsequent injections. Discontinuation of DMPS after the first injection (at a dose of 50 μmol DMPS/kg) caused renal Pb levels to increase until further injection of DMPS, several days later, which again mobilized Pb only from the kidneys. A single oral administration of 150 μmol DMPS/kg (a dose adjusted for specific chelation from the kidney) to rats, previously exposed to different doses of Pb resulted in a significant decrease of renal Pb in groups injected with more than 0.5 mg Pb/kg. A linear relationship was observed between renal Pb burden and urinary Pb excretion following chelation (r = 0.94, p < 0.01). Thus, the specific removal of Pb from the kidney by DMPS treatment suggests a potential use of DMPS, a relatively nontoxic drug, for the estimation of renal Pb burden and also for treatment of Pb poisoning. Unlike other chelating agents, DMPS can be administered orally.