Cadmium speciation studies in the intestine of Lumbricus terrestris by electrophoresis of metal proteins complexes.

Cadmium speciation of the intestinal compartment of the earthworm species, Lumbricus terrestris, has been investigated using polyacrylamide gel electrophoresis under non-denaturing conditions. Worms exposed to Cd(NO3)2 supplemented soils have been studied and compared to control samples. Prior to electrophoresis, the worm intestines were removed and dissected. Proteins in the crude intestinal extracts were separated using polyacrylamide gel electrophoresis. The cadmium distribution in the proteins has also been described. In a second set of experiments, cadmium bound to proteins was first isotopically exchanged with labelled cadmium (109Cd) and then cadmium speciation was performed using gel electrophoresis. Autoradiography of this gel shows an intense band in the contaminated sample whereas this band was absent in the control sample. These results show that one type of major protein has a strong affinity for cadmium in the worm intestinal extract. This type of protein had a migration close of that of rabbit liver metallothionein used for comparison.