Effect of liposome-encapsulated meso-2,3-dimercaptosuccinic acid on mice exposed to lead through drinking water.

Liposomes are the potent carriers of therapeutic drugs for their targeted delivery to the intracellular sites specially when the drug is hydrophilic in nature and is unable to cross the cell membrane. Lead, a major source of environmental pollution, is accumulated in the body system of both animals and humans through reticuloendothelial system, the site where liposomes also get engulfed upon their entry into the body. In view of these considerations, meso-2,3 dimercaptosuccinic acid (DMSA), a potent chelating drug used in heavy metals intoxication, specially lead, was encapsulated in small unilamellar liposomes composed of phosphatidyl-choline and cholesterol (1:1) and used to evaluate its efficacy in lead intoxication. DMSA either in free form or encapsulated in liposomes was administered intravenously (2,62 mumoles/kg, three injections at a gap of 48 hours each, total 7.85 mumoles/kg) to mice which were pre-fed with lead in drinking water (500 micrograms/ml) for one month. It was found that only DMSA encapsulated in liposomes was significantly effective in reducing the level of lead in liver, kidneys and spleen at the dose administered. DMSA either in free form or encapsulated in liposomes also restored the inhibition in blood delta-aminolevulinic acid dehydratase (delta-ALAD) activity. The results suggest that liposome encapsulated DMSA may be preferred over free DMSA for reducing the body burden of lead.