Organ distribution and protein binding of cadmium in autopsy material from heavy smokers

Male heavy smokers were autopsied within 3 days postmortem. Samples from kidney, liver, and lung were taken for analysis of cadmium levels and degree of protein binding within the cytosolic fraction. The levels in lung, liver, and kidney were 0.50 +/- 0.35 (means +/- SEM), 2.21 +/- 0.63, and 17.4 +/- 8.8 micrograms cadmium/g wet weight tissue, respectively. In liver and kidney, approximately 75% was bound to a low-molecular-weight protein whereas the corresponding figure for the lung cytosolic fraction was 56%, a difference being statistically significant (P less than 0.05). After concentration of the low-molecular-weight cadmium-binding protein(s) ( CdBP ) by ultrafiltration and preparative isoelectric focusing in a granulated gel, the cadmium appeared in one single band with pI values of 5.8 (lung and liver) and 6.0 (kidney), respectively. It is therefore concluded that human lung exposed to cadmium, in this case via cigarette smoke, contains a CdBP , which binds cadmium. The relative degree of binding is less in lung than in liver or kidney, implicating that the metal could be more toxic to the lung than to liver or kidney, as the protein probably serves a role in detoxifying cadmium.