Electrochemical study of human foetal liver metallothionein: influence of the additions of cadmium and zinc

Three different isoforms of human foetal liver metallothionein (HFL MT), MT-0, MT-1 and MT-2, have been characterised using electrochemical methods such as differential pulse polarography (DPP) and square wave voltammetry (SWV) at the mercury electrode. MT-0 and MT-2 contain mostly zinc, whilst MT-I contains cadmium and zinc. Therefore, MT-0 and MT-2 behave in a similar manner, but MT-1 behaves differently. These human MTs are not very stable compounds. Studies on additions of cadmium and zinc to them have been carried out. MTs are able to incorporate these added metal ions into their molecular structure, provoking a change in the complexing forms of both cations. In fact, two different polarographic responses due to the reduction of complexed Cd(II), and three responses from the reduction of the complexed Zn(II) have been distinguished. These species are, however, inter-related. The change in pH in a very narrow range, from 8 to 9, provokes important changes in the features of the polarogram and hence in the detection of the different species. (C) 2000 Elsevier Science B.V. All rights reserved.