Metallothionein-like proteins in Macoma balthica: effects of metal exposure and natural factors

Abstract

Biological processes involved in the tolerance acquired by populations chronically exposed to metal pollution in the environment were examined in baltic clams (Macoma balthica) originating from both industrialized and clean areas and in clams exposed experimentally to metals. It has been shown previously that clams surviving Ag and Hg exposure at LT50 did not protect themselves by accumulating smaller amounts of metals than clams that failed to survive, so attention was focussed on the physicochemical forms of storage of the accumulated metals. Silver was found to be predominantly bound to insoluble forms and Cd and Hg to soluble forms. In both controls and contaminated clams, a metallothionein-like protein (MTLP) has been shown to be present, the concentrations of which did not depend on the geographical origin of the clams. The significant relationship between metal and MTLP concentrations shown in the baltic clams suggests that the induction of this protein could provide a useful tool for the biomonitoring of metal pollution. The influence of natural factors (season, weight), however, must be taken into account when interpreting such data.